Hopefully this post will help others with this problem.
I have run into groom scripts that won't finish and can't be stopped manually.
I'm running Retrospect 9 on Mac OS, but I expect this will apply to v8 and likely others.
Delete the .log file for your catalog. See the details below.
After the script had been running for several days with no apparent progress, I was confident that it was hung. I tried stopping it in the Retrospect UI. It popped up the 'are you sure' dialogue and I clicked stop a second time. I waited several hours and nothing changed, the script was still 'running'. I tried re-booting the system, which took a long time because it had to wait for Retrospect Engine to shut down. Once it restarted, the grooming script continued doing nothing just as before.
Next, I stopped the Retrospect Backup Engine in System Preferences. I waited several minutes until it said it was 'stopped'. I unchecked the 'Launch Retrospect Engine on system startup'. and re-booted. Then I went into Library - Application Support - Retrospect - Catalogs. In that folder I deleted the .log file for the backup set that it was trying to groom. Then I started the Retrospect Engine as well as the UI and the grooming script was gone!
I immediately started rebuilding the backup set's catalog. I assume the grooming failed because of an error in the catalog, but YMMV.
I suspect that the .log file represents the progress made by the grooming script. When Retrospect starts it sees the log file and tries to continue where it left off. By deleting the log file, Retrospect doesn't see that a groom was in progress so it doesn't try to continue doing nothing.
In general I find myself having to rebuild catalogs fairly often (several times per year). I haven't seen any recommendation or standard practice suggesting how often this should be done. Should I have a re-build script before and after each groom?
Retrospect works great until it doesn't . . .