We faced two installation issues which broke Jscript functionality in VS 2008 Beta 2
The recommended workaround for both the issues is to Repair the Visual Studio installation by running setup again. The first issue can be avoided by uninstalling SL Tools for VS Beta1 before installing VS 2008 Beta 2. The second issue can also be fixed if you dont mind fiddling with the registry. See the blog post here for details.