If you still use Visual Studio .NET 2003 (I still do for some older .NET 1.1 projects) you may experience following situation:

1. You have an ASP.NET Web project that is controlled by Visual SourceSafe
2. While opening the project Visual Studio 2003 hangs, stops responding to mouse clicks and keystrokes.

Fortunately there is a quick fix to that.

1. Open the registry editor (Start -> Run: RegEdit.exe) and navigate to the following key:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows
   • If there is a value key named “UserPostMessageLimit” change the value to something greater than 10,000 (the maximum is 18,000).
   • If this value key does not exist, right click the
     HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows
     key and choose “New” “DWord” value named “UserPostMessageLimit” (without the quotation marks) and set it to a value greater than 10,000 (the maximum is 18,000).
2. You will need to reboot the workstation for this setting to take effect.
3. Once rebooted, delete the local user’s VSWebCache (this folder should be located in C:\documents and settings\<username>\VSWebCache), then open Visual Studio and retry opening the project.

Source: KB949910