Dude, this game fucks with me all the time, for a while I couldn't do a couple missions in the career mode because I would just fall through the floor and start doing cartwheels in space.
I've found one thing you can do is change profiles or make a new profile, load up a map with that profile, then exit and change profiles to your original character, sometimes it helps.
But if you can even access the menu screen i dunno what to tell you.