Bizarre problem with Windows Photo Gallery

I've had a strange problem pop-up over about the last week.

Any picture I download from a news that's in portrait format, ie upright, is
squashed down to a square, heavily distorting the picture. Landscape pictures
are left alone. It also does this when viewing photo's as thumbnails in
Windows Explorer.

Thyere's nothing actually wrong with the .jpg's, as when I load them into a
photo editor (I use PSP 8.0), they look normal. Also the properties dialog
opened from the right-click menu when viewing a picture shows the right width
& height in pixels.

It doesn't do it with pics downloaded with IE, they view normally.

Does anyone have an answer?