Ok, I have confirmed this to be an IE8 specific issue, related to a bug in IE8:
support.microsoft.com/kb/276228
I was unaware of this IE8 bug before. This bug would affect a number of drop-downs for IE8 users that are created by copying the drop-down list from somewhere else.
I have made a fix in a number of places to workaround this IE8 bug for IE8 users.
Please try again and let us know if this resolves your issue.