The change we made was not supposed to affect existing applications. With no html.useStandarsMode the system should still use the old mode ("quirks mode").
The problem is probably a bug in the code we added to support both modes (mostly related to differences in size calculations). You can verify that you're getting quirks mode by viewing the document type declaration in the source of the page. It should say:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
It will be helpful if you can reduce the problem to a small example that is rendered properly in previous versions and is now rendered incorrectly.
For best results, use the Firefox browser..