Windows EventLog on Vista-problem with category names

I have an event log message text resource dll that also contains category
names. This "event message file" installs and works correctly on XP. My
events are retrieved from the dll and my category names are also retrived and
appear in the event viewer when looking at events generated from my code
VB.Net code.

However, when I install this event log source on Vista, the category names
are not retrieved and just the category number is displayed. The message text
is correctly retrieved from the dll and displayed. The registry configuration
for the category message file is correct as far as I can tell and is the same
as on XP.

There is some difference as on Vista the category is now called Task
Category, but what little info on this I could find suggested they are still
the same thing...the fact that it's not working suggests something is
different...