When you logon with a roaming profile, a copy of your profile is locally cached on the workstation. If the boot partition on the workstation has barely enough freespace to house your profile, the locally cached profile will corrupt.
When you logoff, the corrupt profile is copied back to the server, damaging your permanent roaming profile.
Insure that you have sufficient freespace on all your workstations. Delete obsolete files, compress little used folders, or get a larger / additional disk drive.