(read until the very end).
Had the same problem today. Got the info below from http://www.coastalappliances.com/hintsandtips.htm.
****F2 means that the rotor (PN 525884P) is sensed to not be turning, It could be a small piece of food debris, a tiny fragment of a shell or broken glass, has gotten lodged in the wash impeller, or it could be a seized bearing. The buzzing sound is most likely a burr on the lower portion of the wash rotor. Remove the rack, then the filter plate (the large silver plate with all the holes in it), and then the wash impeller (the blue finned "fan" in the middle). While looking at the lower rotor, be sure that its fins are crisp and sharp with no flashing or burrs. Remove burrs with a razor blade. Does the fan spin freely? If not, try a few drops of lubricating oil on the bearings while working the rotor back and forth trying to free it up. Is there anything in the cup that would prevent the rotor from turning? (fragment of glass, shell, etc)***
In my case, the rotor was stuck not because of any fragments, but because the black cylinder above the magnet (and below the metal shaft that is attached to blue fin which allows the fan to rotate inside the plastic housing, must take all rotor assembly out to see it, not hard at all). Blue fin can be separated out with a bit of pull.
No luck with any lubricant. I used some 400 grit sandpaper to sand down the black cylinder until, with the plastic housing in place, the metal shaft can rotate FREELY (one hand spin should go 5-10 rounds of rotation). My problem is solved.
Hope this helps.
Kam, December 2008