Alright me123, I'm flustered now! LOL!!! Everything that I find on it says that it's been brought to steams attention and that they're "working on a fix". I can't find any solid information on how to fix it, only lots of people complaining about the same error with all sorts of versions/mods of both HL2 and CS:S.
I did find this though...
QUOTE
i just deleted local content and reran it and it fixed everything by itself
(
source)
I'm not sure how to do what this person is talking about though, sorry. If you know what he/she is talking about, you can try that fix if you like.
As far as I can tell, there's either an issue with Steam itself, or an issue with Steam/CS:S conflicting with anothe program that's running.
Do you run just the game itself, and nothing else in the background (like have other windows open including internet explorer)? Also, have you gone into MSCONFIG (Start>Run>type in "msconfig" without the quotes) and unchecked things that dont' need to start when windows starts (
see here for help)? Have you done a few scans to ensure that your computer is free of malware and whatnot, like Adaware SE and Ewido for starters? Have you tried to disable your firewall (if applicable) during gameplay to see if that makes a difference?
Try the above, and let me know how you fare with it. If you still get the error, post back and please let me know. I'll try to see if anyone else has had better results with this issue that you're having!