Jaja I started having problems after installing the latest Catalyst drivers for my 7850; before this I was getting a million FPS, afterwards about 7 :\ so I guess AMD might have derped their DX8 support, thinking nobody plays such old games..
Cowsy's suggestion was to completely uninstall the drivers, then re-install an older version (handily I have several previous installs). Haven't tried that yet because a) I'm lazy and b) the new drivers made a noticeable difference to newer games. However I'm getting ET withdrawal symptoms so I'm gonna try the \com_maxfps 125 and \cl_maxpackets 100 config thing first, cheers for that Baker :)
Quack quack. Will report back once I've tried fixing it.