'vssadmin list writers' command would return no list and ntbackup
generate these errors:

Type: Error, Source: VSS Event ID: 20

Volume Shadow Copy Service error: A critical component required by the Volume Shadow 
Copy service is not registered.  This might happened if an error occurred during 
Windows setup or during installation of a Shadow Copy provider.  The error returned 
from CoCreateInstance on class with CLSID {faf53cc4-bd73-4e36-83f1-2b23f46e513e} 
and Name VSSEvent is [0x80040154].

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Type: Error, Source: VSS Event ID: 8193
Volume Shadow Copy Service error: Unexpected error calling routine CoCreateInstance.  
hr = 0x80040154.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
After searching the web for some time I found several sites with info that related to
these errors but no solutions. Fixes for other VSS errors had no effect.
Finally I used filemon to see if I could identify what was missing, and that worked.

Using filemonitor I determined that 
VSSADMIN is looking for Eventcls.dll in C:\Documents and settings\Administrator 
when it is actually in C:\WINNT\system32

I copied the file over to the C:\Documents and settings\Administrator folder and now
the 'vssadmin list writers' command returns the list of writers and ntbackup works again.

Why this error occured is a long story I am trying to make sense of, it had something to do
with a failed SBS 2003 SP1 installation, the Travan seen as miniqic problem, 
hotfixes, MSDE install failed, missing Outlook install in Client Apps, etc, etc.

Once I figure that timeline out I will write it up.