Gabe,
First thing to do is to make sure that in the VO Utility, Cursor
tracking options, uncheck the VO cursor tracks mouse and vice-versa.
I normally like these on but when using the Accounts System
Preference it causes the silly "System Preferences busy" in nausium.
second, Click the "click Lock to Make changes" button. You will need
to put in your password for that one. the quickest way to get there
is to go left once you are in the Accounts Preference so you don't
need to go all the way around.
Third, once you've navigated to the user that you wish to Delete,
make sure it is selected then press the tab key which first should
take you to the Add user button then subsequently to the Delete user
button.
Works for me, hope it does for you.
Later...
Tim Kilburn
& Carter the Canine
Fort McMurray, AB Canada