Windows Photo Gallery resolution problem

Recently, the majority of image files I've been saving have been

displaying incorrectly on Windows Photo Gallery. The horizontal

resolution for all the images becomes 1 dpi and the vertical resolution

becomes a number like 400 or 600 dpi. The result is images appear as a

flat line when opened in Windows Photo Gallery but are perfectly fine

when opened with other viewers. The icon thumbnails of the images also

appear as this flat line. I don't see anything in the options which can

fix the problem.

Has anybody encountered this problem before or know a solution?

Thanks