Hi scott_mckenzie
As said above by bella Av album art fixer. Excellent app.
Should the issue continue, use Av album art fixer to save time.
It will most likely fix the issue.
Two good applications to have on hand..
For music foldrs: Av album art fixer
http://www.avsoft.nl/artfixer/
For Videos Folders DVD Cover Grabber:
http://www.madprops.org/DVDCover/
Bryce