Hi Jeremy,
Can you try to enable logging for the backup regimes on the
client machine.
To do this, you'll need to create an empty file called "aitrace.log" in the all users' application data path.
There's no environment variable for this location, but if you're running WinXP Pro, the path to the file should look something like:
C:\Documents and Settings\All Users\Application Data\Symantec\Ghost\aitrace.log
Note that the "Application Data" folder is hidden so you may not be immediately visible.
Once you've created this file, can you force a baseline of the client. Once the baseline is complete, this file should contain tons of logging information about the snapshot operation.
Then you can try the incremental backup - and once again, logging information will be appended to the file. I'm assuming that the incremental will fail and fall back to a baseline. Anyways, once all this is completed, the aitrace.log file on the client might contain some clues as to why the operation is failing.
You could probably e-mail the resulting logfile to Adina so she can help you isolate the problem.