i used to get this too. I think increasing sv_timeout helps, you could also try increasing com_hunkmegs / com_zonemegs. I can't confirm what fixed it exactly as I tried a few things at the same time including changing the map sequence a bit. Also make sure you have a blank line or // EOF .. apparently the engine does not read the last line of a config correctly.
It used to happen frequently but now I dont get it at all so it's definately fixable.
