I've had this problem before on another PC, and now I've noticed it on my current one.

When attempt to save an image (either rightclick or save as), the File Save dialog only allows it to be saved as a BMP file and defaults the name to "Untitled" an no longer shows jpg in the file type drop down list and no longer shows the name in the file list.

This is very fustrating when I go to save a wallpaper jpeg from Dev Art for instance