I’m actually working on this as we speak.
I’ve been building a website for a community college… and they only use IE8 internally. I’m very familiar with the issue. It’s definitely an IE8 issue.
I’m close to a resolution. I’ve attempted adding higher z-index’s to parent elements, but the results were negative.
Right now I’ve got it to where the dropdown appears in IE8, but it also expands the entire parent div (the actual main nav menu).
Once I have a solid, reliable solution, I’ll be sure to post back here.