[Lion7718]

This might or might not work...
There are a few times I get a pic with a thumbnail completely different than the pic when it's opened..usually just deleting the thumb.db will fix that, thats a cashe problem...but thats not what I'm getting to...anyway..if you open the file in your photo editing program..change something..I usually run the crop tool across it..than click undo, now save the file. Now when you open it up..it should be ok.
As for the 'No Preview' problem..seen that before also..it's usually from a huge pic..just close it down & open a pic next to it..use the arrows in Windows Fax & Pic Viewer to get to the next pic....it will load, should load..easier because the program is already running...also make sure your not running something in the background that is using alot of CPU.