• Application:  SQL Server Management Studio 2005
  • OS:  Windows 7 Enterprise, 32-bit
  • Error Message:   Unable to cast COM object of type ‘System.__ComObject’ to interface type ‘Microsoft.VisualStudio.OLE.Interop.IServiceProvider’. This operation failed because the QueryInterface call on the COM component for the interface with IID ‘{6D5140C1-7436-11CE-8034-00AA006009FA}’ failed due to the following error: No such interface supported (Exception from HRESULT: 0×80004002 (E_NOINTERFACE)). (Microsoft.VisualStudio.OLE.Interop)  
  • Action:  Occured when connecting to a database server from the GUI.
  • Cause:  Installing SourceGear Vault Client (in my case, 5.0.4 build 18845).
  • Fix: 
    • 32-bit:  regsvr32 "C:Program FilesInternet Explorerieproxy.dll"
    • 32-bit:  regsvr32.exe actxprxy.dll
    • 64-bit:  regsvr32 "C:Program Files (x86)Internet Explorerieproxy.dll"
    • 64-bit (this one I haven’t verified for 64-bit):  regsvr32.exe actxprxy.dll

The following links were helpful in my search to remedy this problem: