You know, thats a side effect of defective hacks (gets suspicious...). Anyway I think I know how to fix your problem. Go to your cstrike folder and check if you have a userconfig.cfg (or if you know you have one, open it). If you don't have a userconfig.cfg then replace the word "userconfig.cfg" with "config.cfg" in the following instructions and go from there.
Check all your settings for userconfig.cfg, make sure the binds are correct and make sure cl_forwardspeed isn't 0, same goes for cl_backspeed. If they are messed up set them both to 400. Now that you've fixed all your binds and speeds make sure your fps_max isn't low and fps_modem isn't 1. That's all for your userconfig.cfg(should fix your problem)