Just was testing on that server on the backwater_t map, then i got deconnected because the game couldn't load wq_backwater_t.bsp.
Then i restarted the game and tried to connect to hika's server again and i got the following message " Couldn' load maps/wq_backwater_t.bsp"
After that i tried it in SP and the map worked. I also tried it on sig11's server and it worked fine,too.
So i think it's a server sided problem.