I've been having all sorts of problems with Gimp 2.8.4 on Windows 7. I can't run Alpha to Logo scripts for example. The input dialog pops up, but I can't change gradients for instance. I've actually reverted to 2.6 for some of my tasks. It's been making this month's challenge extra challenging.

I'm thinking of uninstalling Gimp 2.8 and reinstalling into a non-UAC controlled folder. Just the way it is misbehaving, I am thinking that UAC is somehow conflicting with the individual tools. I'll let you know how it works out.