Can't delete old jobs?

I'm having an odd problem with AR where I can't batch delete jobs more than a year old. When I click "undo previous batch" and select "delete previous jobs" it removes everything from the past year, but instead of deleting older jobs it just files them all under "December 1899" (although the dates of the jobs themselves are unchanged). Is there an alternate way of deleting old jobs? (Besides pruning them one by one - there are hundreds!)

You can manually delete the Undo files. They live in your "appdata" folder:
%appdata%\Hulubulu\Advanced Renamer 3\Data\UndoLists
Just delete all the files in this folder.