I inherited the maintenance of a batch VBA application for word for
manipulation of tables and "cleaning" to desired format.  this app is
intended to run on batch of documents overnight, with  word 2000  in windows
2000.

Now the client has migrated to Xp pro and Word 2002. The vba app is having a
lot trouble in that it does not seem to handle errors and stop processing
Furthermore, when it runs into error, it hogs the CPU ( 99%)..  It also
every now and then cause prompts to merge with such and such.dot (templates)
which is not supposed to.

I was wondering if it would be better to migrate to vbs script or .net
Visual Basic or C# while I adapt the vba to handle exceptions... right now
the vba app is about 7 pages long in code plus a couple of forms.

There are almost too many ways to answer your question. The first issue is
what language will be easiest for you to use. The second lies in
understanding where your program is either too complex or too slow.
Any of the tools you meantion will do the job. Compiled code will almost
always run faster than script--but you can also use combinations of script
and compiled code too. If you're looking to get a jump on things then C# is
a good choice since it seems to be the favored language for .Net development
but if you're familiar with VB then VB.Net might be an easier transition and
their is virtaully no difference in performance between VB.Net and C#. So
like they say at Microsoft "Where do you want to go today?"