Time machine backup problems

[pete burns]

Hi

I have some trouble with backing up with timemachine.

I connected an externeal usb disk to my mac and made a complete backup.
Now I want this disk to be conncted through my airport extreme basestation as an airdisk.

But now timemachine doesn´t recognize the backup, but wants to make a new one.

I imagine its something about the sparsebundle TM makes when backing up to a network disk, but is there a way to cheat it to use the backup allready made? (I have a lot of data and backing up all over again through wifi will take a long time)

Burns