I can't play this game because of the error "Could not load kv6 file." I get it every time I try to load up a server, no matter which server. I've uninstalled and reinstalled several times. Any idea how I could fix this issue?

The kv6 files store the models for the items and entities in the game. Yours haven't become corrupted or anything, have they? I assume you've already tried reinstalling.

Yes I've reinstalled the game several times, each time extracting it to a new location to make sure that wasn't the problem. I'm out of ideas.