[Jon M]

If anyone asked me whether they should install beta software I will always say no. (unless you have the knowledge and patience required to reinstall your operating system and appreciate the risks involved)
The more important the software, the more important it is to stay away from development code.

I'm sorry if that sounds like a sort of "i told you so".. but it was worth pointing out nonetheless.

As far as solving the immeadiate problem is concerned, you might be changing the setting individually.. but are the overall security settings overriding it? (tools -> internet options -> security tab) try setting the level to medium or low