Something has broken with the right side drive wheel spring. The right side wheel no longer has spring tension and the vacuum can no longer manuver. I've submitted a service request (under warrant) but haven't heard from them yet.
An internet search turned up this as a common occurance.
It is a simple fix to replace the spring, but you do have to disassemble the vacuum to replace it. I have replaced mine on the 9250, and have extra springs. Sometimes you can find replacement springs on ebay.