mjkemp

Like markcoppock, I’m in Genesis.
The other solutions did not work, but adding this to the theme style.css worked.
You are better off, I think, adding to a child theme css file, because if you edit the NG sheet it could get overwritten on an upgrade to the plugin.

/*** FIX SQUASHED THUMBNAILS IN NEXTGEN GALLERY IN IE8 ***/
.entry-content .ngg-gallery-thumbnail img {
height:auto;
margin: 0 0 18px 0;
width:auto;
}