https://discussions.apple.com/thread/2800116?start=0&tstart=0
Corrupt disk or files from the looks of it..
Do a full network reboot.. if that doesn't do anything..
Full factory reset of the TC.. make sure you plug in by ethernet and turn off wireless. Do not do any of this via wireless.
No advance then, verify the sparsebundle on the TC. See A5 in Pondini.
http://pondini.org/TM/Troubleshooting.html
After that if you get no progress.. as suggested in the other thread this may be a failing disk. do a one pass erase and try again.. that will wipe out any backups and files you have on the TC.. does that matter?? If so pull the drive out of the TC and see if you can copy the files to another drive.
http://www.ifixit.com/Device/Apple_Time_Capsule
Of course if it is in warranty just get apple to replace it.. the above would void warranty so only if warranty and applecare has expired.