CKEditor 3 Buttons Not Displaying Properly in IE8

I thought this would've been discussed previously but I couldn't find a thread on it (so feel free to just point me to one if it exists...seems 'IE8' is considered a noise word and won't trigger a search), but why do the buttons in the toolbars appear just as rectangles instead of with the nice, rounded edges like they're supposed to?

What's causing this and is there a fix for it?