All of a Sudden, Windows Refuses to Open PNG Images --- But It CAN

All of a sudden, I have started having the weirdest thing going on with Windows 7 Windows Photo Viewer.

I have WPV set as the default viewer ONLY for PNG strictly for convenience and to not mess up wherever I may be in any of my photo editing/viewing programs should I need to view a PNG.

I try to only ever use the PNG format for such things as screen-shots that I save in various document folders with any other information on whatever the PNG pertains to.

Anywhere I look in Explorer, the little icons in front of my PNG files (Details View) are now just blank white, instead of the little Windows PNG icon.

Double-clicking on any PNG results in a message telling me that Windows cannot open this file, etc., etc.
Hi-liting the file and clicking Open in the tool-bar yields the same message.
Likewise right-clicking the file and choosing Open.

Now, this is where it gets weird, I can hi-lite the file and open the drop-down menu by clicking the arrow/button beside Open in the tool-bar; I get over a dozen choices; I can select that same Windows Photo Viewer that has been insisting that it cannot open the file and it will immediately display the image as if nothing were ever wrong.

In that same drop-down menu, I can click Choose Default Program, and again I will get the error message.

This does not seem to affect the ability of any of my many other programs to open PNG files.

I have no idea what I may have done to bring on this weird behavior.

I have not yet tried to see what it will do with a jpeg.

Thanks for reading and all help is appreciated.

Well, I have no idea why the weird behavior.

However, I think that I have fixed it..., although I have no idea just how or why it was so easy.

I will leave this here for the next poor soul who may run against the same situation.

Just out of curiosity, in FastStone (if you don't have it, you are really missing out), I went to FastStone settings and made FastStone the default PNG viewer.

I then took a peek in Explorer and all of my PNG files had the FastStone icon.

I was then able to open the little drop-down menu and Choose a Default Program worked without giving the error message; I selected Windows Photo Viewer and it immediately appeared with the selected PNG displayed.
I checked my little icons again and they were now displaying the proper WPV instead of blank white icons.
I tried several PNGs just to make certain that things were back to normal and everything worked as it should.

So, the moral of this story is, when Windows decides not to open images, follow the procedure described above and all will most likely be well.

I just used FastStone on account of it being lightning quick and very handy to change associations; I am fairly certain that any other photo viewer program would have the same effect.