Right after VS 2005 shipped, a lot of people ran into "Package Load Errors" when trying to install and run the final release of the product. These are often the result of having some left-over VS 2005 Beta or CTP bits that weren't uninstalled completely on the same machine.
Aaron has posted a good blog entry that walksthrough how to clean these old bits off your system if you (or someone you know) run into a package load issue in the future.
Hope this helps,
Scott