Yup, scratch that, tested again in IE8 and it looks fine, ignore what I said earlier!
I also have an issue of it turning into a bright blue in IE9 on hover, rather than a slightly darker orange. I’m also noticing that in IE8 that the button barely appears as a little 3px wide line in the bottom middle of the page…though, I’m using IE Tester to see IE8, and sometimes I worry about how reliable it is. 😛
Amazing plugin otherwise!