Thanks to both of you for your prompt replies. Outlook placed you into my Junk E-Mail folder and I just found you before I cleaned it out.
I double checked my thumbnail size under Options>Preferences and the Thumbnails tab, then re-scanned the tree and there was no change. I then removed the thumbnails from one of the smaller folders and had TP scan it again and, again, no change.
Sometimes I wish I had version 7 back!