As noted on Soma’s blog, the .NET Framework 4 beta 2 and Visual Studio 2010 beta 2 have been released today. If you previously had the .NET Framework 4 beta 1 and/or Visual Studio 2010 beta 1 installed, there are some very important uninstall instructions that you must follow in order to fully uninstall beta 1 so that beta 2 will work correctly.
If you had the .NET Framework 4 beta 1 and/or VS 2010 beta 1 installed, please follow the instructions at http://go.microsoft.com/fwlink/?LinkID=167718 to fully uninstall beta 1 before you install beta 2.
These instructions explain how to fully uninstall VS 2010 beta 1 and then fully uninstall the .NET Framework 4 beta 1. If you do not follow the above instructions, you may see a crash dialog during the installation of VS 2010 beta 2, and you may see package load failures when trying to use VS 2010 beta 2. The instructions linked above also contain steps to repair the .NET Framework 4 beta 2 and VS 2010 beta 2 in order to recover from these errors.
If you run into any issues that are not covered by the above instructions, I encourage you to check out the .NET Framework 4 and VS 2010 pre-release forums for additional troubleshooting suggestions and workarounds.