I have a fairly stable computer system so I usually know when odd behavior occurs. I recently was investigating software that would convert scanned negatives to digital images. I ran across a package called SilkyPix which had a free demo. I usually do not download demos, but thought I'd give this a shot to see how it's conversion worked. After a few attempts, decided it wasn't what I was looking for so I uninstalled. A few days later, when I opened QImage, I noticed strange behavior. My thumbs were gone, QImage hung and then seemed to take forever to change screens. I rebuild the thumbs and it seems to be working well now. Just a heads up, that there seems to be a conflict that occurred with the SilkyPix software and I realize it seems odd that it would have occurred since the software folders involved should not overlap.
Whether this was a one time issue I'm not sure- just a word of caution to other users.