We are upgrading 3000+ machines to 4.91 sp4 and are seeing too many of them bsod'ing on login after the client is upgraded. They previously held a flavor of 4.90 (we ran the gamut of sp versions of 4.90).

I know this was a issue a while ago, but found several tids saying it was fixed in 4.91 sp2. All machines are Xp SP2, is there a windows sp that needs to be applied?

Any other ideas to help troubleshoot?