Somewhere I recently (could've been at the RoombaReview BBS) saw a repair procedure for a broken belt in one of the wheel enclosures. The belt failure caused such a 'circle' problem as well.
Also over there (again, somewhere) is a full diagnostic procedure. I haven't tried it yet.
Amazon has shipped mine, so I'll probably see it next weekend.

Edit:
good list of procedures


Edited by Robotic (06/02/2006 22:40)
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10101311 (20GB- backup empeg)
10101466 (2x60GB, Eutronix/GreenLights Blue) (Stolen!)