I run cleaner on Windows Server 2003, so no idea if XP SP2 breaks it. But try installing (if you haven't done so already) SP2 for cleaner. It fixed lots of issues I had with it.
http://www.discreet.com/support/clea.../download.php3
If it still fails, I suggest you try uninstalling it and reinstalling cleaner, XP SP2 fixes the .NET runtime that cleaner depends on, I had to do that on a few apps that relied on it after updating my laptop with it.