We’ve heard a few reports of cases with VS Orcas Beta2 where ASP.NET controls do not show up on the toolbox and ASP.NET tag intellisense and validation is broken in HTML source view. All of the cases reported so far have been with Vista. The root cause of this is that the Orcas Beta2 version of System.Web.Dll did not get installed correctly on the machine due to interference with some of the .NET Framework Hotfixes that were on the machine earlier.
The recommended workaround is to uninstall VS Orcas Beta2, uninstall any .NET Framework 2.0 or 3.0 Hotfix that you have installed on your machine and then reinstall VS Orcas Beta2 . All released Hotfixes of the Framework have been rolled into Orcas Beta2 so this will not regress your functionality or put your machine in a vulnerable state.
Here are the steps for you to take in order to uninstall your .NET Framework Hotfixes.
1. Go to Start -> “Control Panel” -> Under Programs “Uninstall a program”
2. Click on View Installed Updates
3. Right click on any of the following KBs that you see and select “Uninstall”. You will see these listed as “Hotfix for Microsoft Windows (KBxxxxxx)” or “Security Update for Microsoft Windows (KBxxxxxx)”.
4. Reboot your computer before installing (or reinstalling) VS Orcas Beta2.
This should fix the issue for you. In case it doesn’t for some reason, do let us know.