I just wanted to thank you for the above! I have also struggled with this a lot. Very frustrating! I just wanted to share the solution that worked for me.
Theme Free Responsive from Cyberchimps.
Even though I solved the big issue with the above I still had problems when I opened IE in 125%. So i started playing around with
.et_lb_module img, .tiled-gallery img {
/* max-width: 900px; */
max-width: 1000px!important;
}
and got it working with my theme and IE11 with the following:
.et_lb_module img, .tiled-gallery img
{
max-width: 100%!important;
max-height: auto;
}
Thanks again Jeremy and david.i!