the hack for this to work in IE8 doesn't really work on mine (Win7). This is what I used instead:
Got the same problem.
For some unkown reason it works fine on css3please.com, but not on the site I am working on. ( http://jsfiddle.net/HLRm9/ )
Removing the fallback background-color seems to fix the problem. But I would like to avoid that. =(
IE8 is old browser and its support not actual. According: http://gs.statcounter.com/#desktop-browser_version-ww-monthly-201303-201403 its usage is about 6.72% and constantly decreasing.