Last night I had a serious problem with my netbook. I'm running Ubuntu on a Dell mini with most of the data on an SD card. Anyway, I think the SD card got messed up when the machine went into hibernation, and when I opened the lid I was getting cryptic messages about the drive not being able to mount. I tried the usual tools, fsck, dumpe2fs, gpart, etc. Nothing doing. Everything that was working for other people wasn't working for me... Kept researching the messages I was getting from the various tools:
Block bitmap for group 1 not in group
Bad Magic Number in Superblock
Disk doesn't contain a valid partition table
The last one ended up being the clue. Found a utility called TestDisk and it had me fixed up in less than 15 minutes.
It was able to figure out the partitions based on the good data still on the disk. Then it was just a matter of using the tool to rewrite the partition table and I was back in business!