Time Machine won't find existing backup

Hi all,

I'm experiencinga a rather strange problem - I'm running a MB Air in a Time Capsule Network which I use for backup via time machine.

I can access the TC via Finder as usual, see my backup file, etc. - however TM won't back up any longer telling me:

"Time Machine completed a verification of your backups. To improve reliability, Time Machine must create a new backup for you.

Click Start New Backup to create a new backup. This will remove your existing backup history. This could take several hours. Click Back Up Later to be reminded tomorrow. Time Machine won’t perform backups during this time."

As there are more than 1.2 TB available on my TC it's not a free space issue. I haven't changed the disc's name either.

Any idea???