Sounds like it, I'm gonna run the test on a 32-bit machine in a minute.
I've had similar problems using WDS.

Actually pretty much the same error.
When deploying Windows 7 from a 2003 WDS server (still W2K domain)
The logon account fails.

When deploying Windows 7 from a 2008 WDS server (still W2K domain)
The logon account succeeds.

Deploy Vista or 2008 (R1) from either servers and you don't get the problem.

The error code you get in WDS is simply 0x80070056.
Which relates to exactly the same problem as KiXtart, authentication fails/invalid credentials/password/username.


Unfortunately I am sort of a Maverick in my Company, loose cannon, I'm not even yet supposed to test Windows 7, let alone ask headquarters to makea ticket for it...