Hello Neil,

I've already checked the license on the PDC and it's fine.

Here's what I have in my eventlog.... this the only suspect message I can find :

Automatic certificate enrollment for local system failed to contact the active directory (0x8007054b).  The specified domain either does not exist or could not be contacted.
  Enrollment will not be performed..

I've find some information on this but everybody seem to be stucked with the problem... no solution so far...

Regards,
Alex