I have 2 problems with Gimp under 12.04.
First, frequently just after saving a image, it folds.
Second, whenever I use a tool, the image editing window becomes deselected, and takes with it the 'show on mouseover' menubar at the top of the screen. To get the menubar back, I have to click in the top of the image editing window.
Previous editions of Gimp did not have this tiresome behavior.