I've been working on this problem for a while now, Vista x64 just isn't updating from my WSUS server.
I've got 26 XP pro workstations and 1 other Vista Business installations (x86) working fine with WSUS 3.0 over 2 domains, which indicates the GPO is set properly and all WSUS settings are correct.
the Vista x64 computer hasn't reported in for over 120 days and is apparently stuck at 88% (not so).
When I run ClientDiag.exe I am getting an error (attached) that I haven't come accross before. I've tried forcing check ins, i've also ensured the Autmatic Updates service is running with correct permissions etc etc.
Any help would be great!