It's a bug in your OS probably. Get a full recursive dump of the page (all JS/CSS/Images), and host it somewhere. Then, try to reproduce against your version.

It's a bug in your OS probably. Get a full recursive dump of the page (all JS/CSS/Images), and host it somewhere. Then, try to reproduce against your version. If it reproduces, simplify the page until it goes away. Try to narrow it to the simplest addition/deletion that changes it from working/non-working. If the page does AJAX after loading, you might have to record and fake playback of whatever it fetches (if it's dynamic)