Hmm. Well, my first thought would be that your keyboard input is getting fouled, somehow. First thing to try would be to edit your defaultOptions.xml file in a text editor of some sort, and replace UseMouse="False" with UseMouse="True" . That should turn the mouse on by default; after that, see if you can click on Options, or anything else on the main menu. If you can get the options screen to load, then try rebinding your keys, and see if that lets you get your keyboard stuff working.
If that doesn't work...well, I'm not entirely sure where else to go, from there. I've got a spare PC or two around here, I'll see if I can't get a box up to test this issue locally.