Make sure the game is patched to the latest version and that all of your device drivers have been updated, this particularly goes for video drivers, as well as any mouse drivers and software. Run the BFBC2Updater.exe in your Battlefield Bad Company 2 folder to update the game.
Fixing mouse performance in Battlefield Bad Company 2 PC can also be done by adjusting video performance and watching latency. If the game seems choppy in general make sure your PC meets the recommended minimum requirements and try lowering video settings to improve performance. In multiplayer, try to play on servers with low pings.
If the issues persist, try checking the Battlefield Bad Company 2 PC EA forums, as the community often posts solutions to a number of problems or try contacting technical support.