PNG Files no longer showing thumbnail

PNG files are no longer showing thumbnails in the
folder 'thumbnail' view. JPG's, BMP's, TIF's, etc are all
showing thumbnails fine. Click on the file, it *does*
show an image in 'preview' in the "My Pictures" folder.
Suggestions?

For anyone viewing this with a similar problem, try
Start/Run regsvr32 /i shdocvw.dll & press enter. Or
regsvr32 actxprxy.dll, enter then restart. If neither
works, check your registry (regedit) & make sure that PNG
(or whatever format is having the trouble) has the same
strings/values as a format that is working. That is what
I had to do, just copy the string identically. After
that, my thumbnails came back. Make a backup of your
registry beforehand just in case you make an error.

-----Original Message-----
PNG files are no longer showing thumbnails in the
folder 'thumbnail' view. JPG's, BMP's, TIF's, etc are
all
showing thumbnails fine. Click on the file, it *does*
show an image in 'preview' in the "My Pictures" folder.
Suggestions?
.