I saw some reports of different components not rendering properly anymore. Have you tried using the new meta tag that is supposed to make IE8 render pages the way it used to in previous versions? Put this in your page <HEADER> tag. Make sure it's the first meta tag in the header.
<
meta http-equiv="X-UA-Compatible" content="IE-EmulateIE7" />
I don't have IE8 beta myself yet so can't test this but it would be interesting to see if it makes a difference.