4.2.1 failing at the preparing stage

Hi,

was working on the old version fine,

get through all the stages on the new until iTunes spends about 5m at the Preparing Apple TV for restore point, then bombs out with this error:

The Apple TV could not be restored, an unknown error occurred 1601

Tried 3 times so far, will try a couple more.

I have just tried restoring it in itunes to 4.2.1.

tried the j/b again still failing at the same point

i haved SHSH backups, and using tinyumbrella to provide local server

but i get error 1600 at the end? any ideas?