Christian,
My documentation says:
10351 errors (Server user id %d is not a valid user in database ’%.*s’) indicate a permissions problem. If the database was loaded from another server, the problem may be due to an incorrect suid/uid combination in sysusers. Check syslogins entries in source and target server, respectively.
Also
If you have a copy of master..syslogins in bcp native format then restore that table too.
You may need to delete most logins except sa & probe.
Regards
Kiran K Adharapuram