After much frustration and searching around, I've finally tracked down the issue here. In between times I scheduled a support call with Cart Throb who were super helpful, so thank you to them for offering their input - it was their advice that set me off on the right track.
In the end however, it was an IE specific issue related to Magic Zoom, a Javascript image zoom feature we'd added to the site. Although this states full compatibility with IE6+, and we've successfully used this before without any issues, it was, believe it or not, the stylesheet provided with it that was causing the problem.
Within the stylesheet were 3 references to cursor
linking to a .cur
file (also provided).
.MagicZoomPlus, .MagicZoomPlus:hover {
display: inline-block;
cursor: url(graphics/zoomin.cur), pointer;
outline: 0 !important;
font-size: 0 !important;
line-height: 100% !important;
direction: ltr;
max-width: 100%;
}
I eventually noticed the cursor wasn't appearing in IE compared to sensible browsers, and removed the .cur
references and voila! Items added to the cart and all working as expected. I can't say exactly why this was causing the problem, but I'm happy enough to see it working again and just set the cursor value to move
.
Thanks for everyone's suggestions in the comments :-)