The error message doesnt seem familiar (prompt error, eh?), but as far as i can tell you, this is normal. Both hl and cs both use the same engine, so it has nothing to do with retail cs. Basic trouble shooting would involve changing video mode to opengl (ignore the warning), and/or reducing the number of bots (8 should be enough). Half life eventually "crashes" after a while no matter when or what im playing, keep in mind this is 1998 technology. Your comp specs play a role in this also, on my old 350mhz hp it would crash after about an hour. With my new 2.53ghz dell, it barely ever crashes, unless i have been playing for a while, im hosting a full server with many people, or alot of processes are running in the background.
EDIT: I misread the thread, i thought you said the error was prompt error (stoopid me). If it says "hl.exe has caused an illegal operation" (assuming you are running windows), this is even more normal. Its just window's way of saying "I cant fix the error, but ill tell you anyway". Grr.....