OSX keyboard issues have been cropping up a few times lately. Some people experience an inability to play or record any notes via the keyboard (as in this thread), while other users experience seemingly stuck keys (or behaviour related to this) that cause the cursor to move automatically, etc. There have also been some email support requests reporting similar things.
In each case I have suggested the logout/login trick, which seems to ‘fix’ whatever was ‘broken’, but I get the feeling that there may be more to it somehow.