It means that there are bugs in Mavericks.
The down and dirty fix:
Make sure that no other Macs are backing up at the time
Pull the power cord from the back of the Time Capsule
Count to ten slowly
Plug the power cord back into the back of the Time Capsule
Wait a few minutes and try another backup
Please report on your results
Or, post back if want to try a bit more elegant "fix"