I would guess it has crapped out. Find out the brand and model number (should be on the sticker inside the cover, then we can help figure out what to do. It is most likely a single unit with the converter behind the breaker panel. Some models you can replace the converter section without replacing the breaker/fuse panels, others you have to replace the entire unit. They are not outrageously expensive, usually in the $200 range depending on the number of amps.
Aaron