You try deleting your "clientregistry.blob" ? It's in the root of the counter-strike folder. Give 'er a shot. Also, save a copy of your config to your desktop (to keep as a backup), then DELETE the config in the config folder. Start the game without a config, it should auto-generate one for you. This trick has worked for me.
If you don't know where any of the files are:
clientregistry.blob -> C:/programfilesx86/steam/clientregistry.blob
your config -> C:/programfilesx86/steam/steamapps/YOURNAMEHERE/counter-strike source/cstrike/cfg/config
Should any of this work, and you're ok finding servers again, exit any games and close steam. Once Steam is closed, you may replace the generic config with the backup you saved on your desktop, and try again. If it fucks up again, send me your config, and I'll find the corruption - IFF that's the issue.