Annoying Picasa 3 Error

If anyone can help me with this, it would be appreciated.

My problem is this. I downloaded Picasa, and set it as the default photo viewer for all my photo types, jpg, png etc. If I attempt to save an image with a custom name, for example, renaming the picture 'sunset001' from what it was, 'sunset20%bright'. If I do this, it somehow voids the image type.

Simply put, I can download an image of any type if I don't change it's name. But, if I change it's name, I have to put .jpg or .png on the file or else it will lose the file type. By lose the file type I mean it save it as an unknown image file.

If I turn Picasa's default viewer off, it stops. But, I want it to be the default viewer, is there anyway to fix this or is anyone else having similar trouble?

If I haven't been clear let me know.

Thank.

~FoV~