Adrian,
Here is what we need you to do.
First quit Photo Mechanic Plus. Make sure there are no lingering pm-task processes running. Open the Activity Monitor and click on the "CPU" tab. Then in the search field at the right side of the toolbar enter: pm-task
If you see any listed, click on them one-by-one and click the Stop button (looks like a hexagon with an X inside it.) You can now quit the Activity Monitor.
Now open a Terminal window. The Terminal application is in the /Applications/Utilities folder. When the window opens type 'cd ' without the quotes. That's the letter c and d followed by a space.
Then in the Finder, find your catalog folder and drag and drop it onto the Terminal window. Next click in the Terminal window and press enter. Your terminal session will now have its current directory inside your catalog folder.
Next copy and paste the following into your Terminal window, and press enter:
time sqlite3 catalog.pmdb "pragma integrity_check"
When that finishes, copy and paste the following into your Terminal window, and press enter:
time sqlite3 catalog.pmdb "analyze"
When that finishes, copy the output of both commands and paste them in your reply to this post.
Thanks,
-Kirk