Do ASP.NET applications created on your PC work on your PC? If no, do the following:
go to command prompt and navigate to the .NET framework directory. It should be c:\Windows\Microsoft.NET\Framework\Vxxxxxxxxx
Run the following command line executable
aspnet_regiis.exe -i
Restart your PC.
and try to open a project you want.
If still the error persists, please paste the error message with any error code that you get.
Take a look at your web.config file in the web project you are trying to open. Have you changed anything in it prior to closing visual studio without trying to start it first. I had the same problem but solved it by removing a faulty httpHandler tag.
I added the tag, built the solution and closed my studio before running the web app. When I wanted to reopen the solution with the web project I got the same error you described. After removing (or better correcting) the httpHandler tag everything was back to normal.
Skype is a telephony/chat application.
Cause of problem :
When Skype starts-up, it stopped IIS website service OR it prevented IIS website service to startup. I don't know exactly which one. My colleague told me that it's due to Skype wanting to use port 80 which is used also by IIS website service. But sometimes Skype uses other ports. If it uses other ports, then problem would not occur as it did not "snatched" port 80 from IIS. You need IIS to be up before you open/create a web application/web serivice project in V.Studio.
Medicine :
1) close Visual Studio .Net & Skype.
2) Open up Control Panel > Administrative Tools > Internet Information Services > [expand the tree and you shall see that your website is stopped. Look for the red "stop" icon.]
3) You need to start this web site. click on the "play" button to start it.
4) Now you should be able to start your Visual Studio solution.
5) Start your Skype if you want to.
6) If you do not want this problem to recur, there is a config in Skype that lets you tell Skype not to try port 80. Uncheck that check box.
We all know that the error msg given by Visual Studio is vague and thus, not helpful. I believe there are many other causes that cause VStudio to display this SAME error msg. :(
Good Luck. :)
The VSWebCache folder is created automatically by Visual Studio when you open/create a web project and can be found in <root>\Documents and Settings\<user>\VSWebCache\<machinename>. Simply delete this folder and VS will recreate it when you attempt (now successfully) to open the web project.
Pedro Bernardo - Povoa Sta Iria