I've got a MacBook Air that has been successfully backing up via Time Machine to my Time Capsule hardrive. Since I updated to Mountain Lion I'm getting the following error:
the backup disk is not in mac os extended (journaled) format which is required
When I google around it looks like this is a common error for non-apple hard drives (b/c they're formatted in FAT, or something else non-compatible), but I'm not finding anybody else having this problem with a Time Capsule drive.
Other than the backups not working, the drive (and router) seem to be functioning perfectly.