Help! Blender 2.5 Acting Weird

Ok. I have been working in Blender 2.5. Everything was going fine for days, but today all of a sudden after opening a few files my Blender won’t let me deselect (A key) or do some other things. I realize Blender is still in Beta. The funny thing is that it’s been working fine for a couple of weeks up until now.

I looked under (Menu > “Open Recent”) and there are 9 files I’ve opened recently so I was wondering if Blender holds these in Cache and if this could be the problem? Do I need to empty the Blender cache?

Any help is appreciated.

Blender 2.5 Build #265845.
Mac OS 10.58 (Octocore)
12 GB Ram