Tim,
Due to a problem in even the latest build of Photo Mechanic Plus, which ends up creating batches of operations that are too large to process, you'll have to follow these steps:
1) Stop the tasks in the Catalog Status window.
2) Quit Photo Mechanic Plus.
3) Delete the cat_state.db : In the Finder, use the "Go to Folder..." command on the "Go" menu. In the dialog box that appears, enter the following path:
~/Library/Application Support/Camera Bits, Inc/Photo Mechanic/catalog/state
(you should be able to copy and paste the above path.)
Then click the "Go" button and after the window opens to that path, select all files in that folder (things with the name cat_state.sq3 or starting with that name) and delete them.
4) Reopen Photo Mechanic Plus and click the "Reintegrate Forgotten Catalog" button in the Maintenance section of the Catalog Management window for each catalog that you have.
This will take a while. Until we address the underlying issue, please refrain from using the "Choose new location..." item in the Folder Paths sub-tree of the Browse tree.
-Kirk