Wow this one has me puzzled, but it's late...
Ok all of those having this error, I wonder if it could be some type of security setting causing this? Do you have full Admin Access on this computer? Also do you have a firewall running, if so the one with SP2 or a 3rd Party one? If you have a Firewall running and it didn't popup a message saying that this application is trying to access the internet, you may need to go in and manually allow this program to access the internet. Attached is a screenshot of the IE Tools, Internet Options, Advanced window showing the JIT.
Also you may want to try this download 1st,
http://www.microsoft.com/downloads/d...displaylang=en
and this one 2nd.
http://www.microsoft.com/downloads/d...displaylang=en
I am not getting anytype of error like this but I am running the .Net 2.0 Beta 1 on my system.