just to quickly clear up the possibility of network RAM: what is the make/model of your gateway? if you're running on a multi-part system, what are the makes/models of your routers/switches/modems?

otherwise, i doubt that's the issue anyway. here's what i need to know next:

obvious question, but have you updated your chipset or BIOS?

how many hard drives are installed? are you running on RAID (include the number) or IDE (SATA or AHCI)?

if you have multiple disks/partitions/drives, is your OS loaded separately from steam?
what are the read/write speeds of your drives?
what are the results of the SMART check pertaining to the health of your hard drives?

how much paging file size have you allocated (System, Advanced System Settings, Advanced, Performance -> Settings, Advanced, Virtual Memory)

what OS are you running?

do you have Windows Aero enabled? (disable it if so -- go into Control Panel, System, Advanced System Settings, Performance -> Settings, Visual Effects, and Adjust for best performance)

what is the security level of User Account Controls set to? (always beneficial to disable it when debugging a choke)

what programs start up with your computer? (if windows 7, go to start & search for msconfig, then go to the startup tab -- if windows 8, go to task manager & go to the startup tab)

immediately after booting (don't do anything besides the following), load steam & tf2, then dump the results of your task manager to a text file: http://www.intowindows.com/how-to-generate-text-file-list-of-running-processes-in-windows/

what is the rate convar set to on TF2?
upload the contents of your cfg folder so I can take a look.

what anti-viruses are you running?
disable any antiviruses, including Microsoft Security Essentials, for now
disable your firewall for now as well

make sure that cl_disablehtmlmotd is set to 1

some rudimentary ideas before i get the above info:
clean your demo folder for now

set rate to something much smaller for now, like 20000 (some servers will overload your NAT table -- if you have a small amount of RAM on your networking device -- if you don't throttle your rate)

unlock the true administrator account and try to run TF2 on it: http://teamfortress.tv/thread/15451/solved-mumble-overlay-doesnt-show

check fragmentation of your hard drives. defragment if there is any fragmentation, but also make sure that you're not automatically defragmenting your hard drives

run a DPC latency monitor in the background every time you play TF2, and stop it after the issue occurs: http://www.resplendence.com/latencymon

if your DPC spikes up to a level that the program alerts you about, then report the results & implement the advice in the following guide: http://www.overclock.net/t/1433882/gaming-and-mouse-response-bios-optimization-guide-for-modern-pc-hardware-2014-r0ach-edition (take the tone with a grain of salt -- ignore advice about disabling Hyper Threading and legacy options)

really unintuitive performance enhancements:
make sure that you've run the Windows Experience Index test
disable (and/or set to manual) any unnecessary services: http://www.blackviper.com/service-configurations/black-vipers-windows-7-service-pack-1-service-configurations/ (he has them for windows 8 as well)
ensure that windows is activated & that you've fully updated windows

if your TF2 is not loaded on an SSD with decent read/write speeds, here's a really shitty workaround for now until i can analyze your info:
offload TF2 to a RAMdisk and report the results

this may seem ridiculous, but have you tried wholly reinstalling the game? this means cleaning all instances of tf2 both from all the steam sub-folders & the registry.

just wondering because of your phrasing; you said you've "deleted your custom folder", which doesn't necessarily mean that you've tried running a clean install in a while. that said, i'd also like for you to recall what, if any, custom files you've put in your custom folder since/before this issue started occurring.

this sort of information would be the absolute best way to set a frame of reference. although the issue is seemingly periodic, there can be a host of factors that exacerbate a core fault, such as IO choke, fragmentation, or even network choke, such as running out of RAM for your NAT table.

again, don't mean to be unhelpful by asking that. when i last had this issue, it didn't go away by simply clearing out my custom files; i had to do a completely clean install.

just trying to figure out each step in this diagnosing process.

consistently gets 500+ dpm as a scout in open pugs
why isn't he in a team yet????

this can happen when you have an improperly packaged vpk or you've unpacked a vpk.
first, do you have any files in your custom folder and/or have you tried installing any custom files (including HUD files) to your tf folder?

i last had this issue when i tried using the original nohats mod on the steam forums.
my tf2 was also offloaded to a drive separate from my steam installation at the time, so it could be a mix of independent factors. is that your case?

why isn't he in a team already
plz help

hi

if you're running through dual stack, your NAT is definitely causing the incompatibility; as you know, dual stack lite allots ipv4 control to the service provider, encapsulating it into an ipv6 stream and sending it back to the end-user. this means that direct ipv4 connections (port forwarding) is technically left in the hands of the provider. i have quite a few ideas as to how to workaround it, but i have a lot of homework to get done before the end of break. i'll add you on steam to discuss further.

explain how you are connected to the internet:

are you connected to a gateway (router/modem combination), or are you connected to a multi-part system (like a router that connects to a modem, or a switch that connects to a modem, etc.)?

what kind of connection are you on (DSL, Fiber, Cable, Satellite)? who's your ISP?
if DSL, how are you attenuated (VCI/VPI numbers -- this can usually be located in the advanced panel/WAN of your connection settings)? don't worry about it if you don't know; the rest of the information can help me guide you to figuring out more advanced info.

what are the makes/models of your router/gateway/however you're connected to the internet?
if you can find them, what firmware version(s) are you running?

are you wired or wireless?
what's the make/model of your NIC/wireless adapter?

what's your computer's operating system?

have you run any malware checks recently? if so, with what programs?
do you run any programs that modify your hosts file (Spybot: Search and Destroy, for instance)? in other words, do you run any "website immunization" programs?

do you run any "registry cleaners" or "game boosters"?

do you route your connection through a VPN or a proxy?

i'm going to need a lot more information than that to provide any sort of helpful advice, but these broad specifications will give me a basis to work with.

knowing that disabling your computer's firewall helped find servers, and knowing that you can't manually connect to any servers, one hunch i have is that you're running through a double NAT, but i need the above information before we can continue on that assumption.

a few really basic ideas before we go deeper:
run your IP through http://www.spamhaus.org/lookup/ and tell me the results
switch your DNS to a public DNS, like google's or OpenDNS.

such beautiful dedication
what a man to behold

pro

one of the best upcoming scouts
idk why 4's drama is even a thing on tf.tv lol

definitely deserves a chance in open.

i felt really bad for laughing at the caster's mumble crashing, but it was perfect

gliss to get 2 aces in first round
better believe it

h5 to kier

good player good man good face