RUNAS has stopped

:System:
HP dc7600 Desktop
Intel Dual Core 3.0ghz
XPsp2
1.5gb RAM

:Problem:
Since the morning of 21st May I have been unable to use RUNAS. I use
it heavily in both explorer, from the command line and for frequent
used cesktop shortcuts. The information entered is simple "runas /
user:DOMAIN\USERNAME mmc"and the account information is correct. I
have tried multiple ways of using runas from a command line (see end
of post) but it gets me the same thing nothing - no errors on screen
or in event viewer, no CPU usage, etc... bugger all happens.

:Action Taken:
Very little I'm afraid. I have ensured Secondary Logon is running.
MMC is in the right directory and RUNAS does exist in the dllcache. I
have replaced the RUNAS executable. Accounts are not locked out and
no changes have been made.

:Solution:
Suggestions welcome.


runas /user:DOMAIN\USERNAME "c:\windows\system32\dsa.msc"
runas /user:DOMAIN\USERNAME c:\windows\system32\dsa.msc
runas /user:DOMAIN\USERNAME "dsa.msc"
runas /user:DOMAIN\USERNAME dsa.msc
runas /user:USERNAME@DOMAIN.ROOT.ADR "c:\windows\system32\dsa.msc"
runas /user:USERNAME@DOMAIN.ROOT.ADR c:\windows\system32\dsa.msc
runas /user:USERNAME@DOMAIN.ROOT.ADR "dsa.msc"
runas /user:USERNAME@DOMAIN.ROOT.ADR dsa.msc

I have tried different accounts, not just my own.