Seems others have this problem too. I looked up online solutions and they told me to set useMouseDamp = true, but I didn't even see that option in the config file.
I also uninstalled and reinstalled the game files to no avail, what's up?

You can add the line, but make sure you're editing the right User.ini (there's a separate one for every Windows account).
It's all in this thread:
http://www.gog.com/forum/the_witcher_2/mouse_simply_not_working

There's only one User on my computer, changing the file didn't seem to do anything.

Unresponsive mouse can also be connected to other input devices like game pads. Disconnect all USB devices, reboot your PC and start the Witcher with only your keyboard and mouse connected. Even try disconnecting your mouse once.
Some users seem to be able to fix this by reinstalling, but make sure to delete all config files, that might remain after un-installation (especially in My Documents; But don't delete your savegames there if you want to keep them).