Error inherited to Blender 2.5 and persist after re-install

I have a very odd problem. [ Blender 2.49b-OSX-10.5-py2.5-intel ] I don’t know what happened but all of a sudden the mouse navigation mmb (rotate) mmb/shift (pan/track) stopped working and became some version of the num-pad navigation exept I can’t rotate up or down. If I click the mmb once quickly it seems to lock that point in and I can zoom in and out by moving the mouse right or left of this point.

Now here is where it gets interesting. I am new to Blender so I assume that I pressed some secret key-combination that started this. After trying any combination of user settings I could think of I restarted Blender 2.45b but the problem was still there, So I opened Blender 2.5a and sure as anything the problem was also there ( a whole other program!) I now delete both versions of blender, get a fresh download of 2.49, install it and presto! the problem is still there!!! after doing some serious googling and such I find out about the .b.blend file and delete that one as well. But still the problem persists.

I have made sure it is not the mouse. It behaves normally in other programs and I have tried several different mice.