Hi Cleo:
First off, let me say that it's many many years since I last used PSP, so I'm far from being an expert. However, I've done a bit of digging and think it may solve your problem if you reset PSP back to the default settings - there is a very similar procedure for when Photoshop starts acting weird, and it usually fixes the problem.
Here is a link to a page that describes how to do it (the section titled
Resetting PSP to default):
Tips And Tricks For Using Paint Shop Pro Eklektik*Kolord*Dreamz
The technique mentions PSP7, but I'm hoping that it'll work for later versions.
I suspect that uninstalling and then reinstalling doesn't actually overwrite the registry settings, which is why you still had the problem.
Hope this helps.