hmm, that's a tough one...I can think of two possible reasons, although I could be entirely off base as wellare you using a compositor like Kwin or Compiz? Compositing window managers often have their own keyboard shortcuts that can interfere with software shortcutsor possibly, because it is a laptop, something involving a touchpad could be causing an issue, although I can't imagine whyI know that's not much help, but it's all I can think of at the moment
But yeah, you may want to downgrade one level with GIMP until the next time it's updated...
I was sorely tempted to install PlayOnLinux and load up my trusty old Paint Shop Pro 7
What's stopping you? I still cannot wrap my head around GIMP... I use Fireworks 8 in Wine to make all of my graphics... If you are accustomed to PSP7, USE IT!