O.K. sorry, some more details:
- the user has to be a domain key
- the user has to be granted to access the \\Server\x$ shares
- the user needs write permissions on the current Directory (e.g. c:\temp)
- the user needs read, write and delete permissions on the source and the target paths
- the user has to be granted to take backups/dbs offline on the source server
- the user has to be granted to restore and attach databases on the target server
using default instances don't make problems in my tests.
@mprokop04: is your source database still online?