http://www.microsoft.com/kb/bussys/winnt/q148485.htm
First, check to see if your system is running Windows NT 3.51 with SP 4. Enter the winver command at the DOS prompt to see what version your system is running.
If you are running Windows NT 3.51 with SP4 and have either reinstalled ClearCase over an existing install or applied a patch to ClearCase since applying SP4, you will need to apply the Microsoft hot fix for the problem, reboot the system, and reinstall ClearCase and patches.
The Microsoft hot fix can be found at:
ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/nt351/hotfixes-postSP4/SMSS-fix
This bug is not known to cause any problems with MVFS databases, but it does cause ClearCase to fail in unpredictable ways.
If you have any questions regarding the situations discussed in this Technical Bulletin, please contact Customer Support at support@rational.com or (781) 676-2450 in Massachusetts or 31-23-569-4310 in the Netherlands.