SitngusOk, sometimes it works for me, sometimes not, I don't know whats the issue. I have to reboot pc/game couple of times to make it working properly again
you probably are not preloading properly
download this map: http://fakkelbrigade.eu/maps/preload_room.bsp
and put this into your autoexec:
map_background preload_room; wait 10; disconnect;clear