Well if it takes forever to run, try dangling a Twinky in front of it see if it runs faster then
Seriously though, yeah its happened to me before. For me its usually an indication I've bout used up my RAM and its time to save and restart. Never timed it though, 5 mins. seems longer then I've ever waited.
Sorry Buzz, not much help.
Hope it works out, and you can get that silly fat Gradient tool in shape!