I had this exact error in Fedora 19. See here...
viewtopic.php?f=4&t=9417I tried lots of things to fix the problem, including a "complete" (system folders included) wipe and re-install of GIMP, all to no avail. I was also having issues with Firefox and in my case, I determined there was corruption in Fedora 19 and a complete re-install was in order. F20 was just released, so I went ahead and dumped Fedora 19 for a fresh Fedora 20 install. After that, my problems went away (knock wood). I hope it doesn't come to the point with you where you have to reinstall F20. You could install another copy of F20 in a VM and test to see if it works on a clean, updated install. That would rule out corruption issues.
I do believe there are memory management issues in GIMP 2.8.x, but my evidence is anecdotal.