This is why we need the Shuttle back in action ASAP, from CBC:

Ed Campion, a NASA spokesman at the Goddard Space Flight Center outside Washington, D.C., told the Associated Press Saturday that he was hopeful the problem on the space-based telescope could be fixed from the ground.

NASA experts suspect a faulty transistor or perhaps a cosmic event has wiped out part of the camera's memory. The transistor can probably be replaced by a back-up unit, while the camera's memory can be reloaded.

"Both possibilities are things that can be resolved here on the ground," Campion said.

Hopefully it can be fixed from the ground, but if not then the satellite will be up there for months, if not a year before a Shuttle crew could get to it and swap out any faulty components. That sort of downtime is insane considering the state Hubble is in anyway.