I have about 5 images out of about 48 taken over the last year and a half that I couldn't solve either through the internal matching system, or the astrometry system. All of the 5 get about 98% to finish, then the timeout pops up at 5 minutes and they don't complete. Adjusting the timer to 8 or 10 minutes would help on these difficult images I'm guessing, but don't know for sure. If you want to take a look at them, I can put them in a download for you.
Thanks,
Andrew