I use the mouse left handed, but in the game it defaults to the standard mouse button settings. Is there a way I can switch it or can you make a fix to use the windows settings for the mouse buttons? Thanks.

Our artists use left-handed mouses too. Usualy they exchange buttons in windows. Does such solution fits to you?
If not, we, of course, will try to make such option in the one of nearest patches.

I think what he's saying is that he's configured Windows to use a left-handed mouse, but that these settings aren't effecting Massive Assault.

ok, I've investigated this question.
The only mouses with special drivers (logitech, miscorsoft) allows to exchange left and right buttons. Switching buttons using Windows stuffs has no effect.
We try to fix this porblem with nearest patch.