It's AOL 9.5, to be more precise.
A little window, titled AOL Uninstaller', has just popped up behind the 'Please wait while uninstalling' box. It tells me 'The search has already been run. Please restart the AOL Uninstaller if you wish to search for older AOL versions again'.
I wish nothing of the sort, never wished it, and have no idea why Vista thinks I did. I can't find a way to close that box, but as the progress bar's still doing its left-to-right animation in the 'Please wait...' box, it doesn't seem to have halted the proceedings.
Perhaps I should have put 'SOS' in the title!