Before I begin I have to apologize for the incredibly useless title for this bug - I couldn't think of a good way to summarize this bug.

The problem I'm encountering is that the entire UI of Gimp 2.8 occasionally will begin behaving oddly - things such as highlighting buttons that the mouse is hovering over will simply not work, and some buttons will become entirely nonfunctional. This will happen nearly constantly, providing a huge inconvenience each time it occurs. This bug will affect every window that the Gimp uses, including dialogs such as the 'Scale Image' dialog or the 'Save Image' dialog and even the 'About' dialog.

The following steps will trigger the bug on my system:
1. Start the GIMP
2. Create a new blank image
3. Draw on the image with the paintbrush tool

After this, various features won't work - for example, if you were to hover over a text field (such as the brush size field) the mouse cursor would not change to the vertical arrow (indicating that you can drag the slider about to change the size of the brush), nor would it change to the I-beam to directly type in values. The rest of the UI will affected similarly.

One interesting tidbit is that the focus will move onto buttons, even if they don't respond to a mouse click at all. This makes me wonder if this may be a bug within GTK instead of the GIMP. I did try configuring GTK to use the default theme instead of the MS-Windows theme, but that didn't have any effect on the bug.

My system is as follows:
Windows 7 Ultimate SP1 x64
AMD Phenom II X4 955
4GB RAM
AMD Radeon HD 6850 1GB, Catalyst version 12.8