10.1 not opening 10.0 mxds

I just loaded 10.1 onto my machine today and cannot load my old .mxds from 10.0
At first 10.1 will open to a white screen and it appears to be thinking and then it just hangs.
My office mate loaded 10.1 onto hers last week and works fine. Do I need a service pack?

Thanks,
philphil