Upgraded from 2.2 release to 2.2.1rc2 (build 331) on Mac OS X 10.4.2 this morning. After I restarted, upgraded the repository, and re-opened my solution, the form I last had open (and was open during the upgrade) was blank. Any attempt to bring it up would continue to display the previous form until I did something to refresh the window (like click or drag the mouse around), at which point all the refreshed areas were blank. Its methods still existed in the editor, but I could not expand its disclosure triangle to see if any elements were there (it would not open when I clicked).
Now, oddly enough, the software update dialog showed again at startup even though I had updated to the latest version. I canceled at the time, and confirmed that rc2 was shown in the about dialog. Now, as a last-ditch effort, I went to Help->Check for New Version and let it update. After a restart, my form was back again and Help->Check for New Version displays no new updates.
So, perhaps something didn’t get updated correctly the first time? I didn’t get any error messages.