Roaming profiles won’t update/delete

I’m having a problem with roaming profiles on NT 4 sp6a workstations. Although all accounts are configured correctly for roaming profiles, some don’t upload to the server at logoff. These same profiles can’t be deleted from the local workstation. The delete button on the System|User Profiles page is greyed out for the offending profile until the workstation is rebooted.

I haven’t found a pattern as to which account/workstation causes the problem. As far as I can tell they are all setup the same.