Why your Visual Studio add-in fails to load with error 0x80004005
Writing Visual Studio add-ins gives you the power to do some impressive things within the IDE to enhance your productivity. Unfortunately getting your add-in to load into Visual Studio can sometimes be a pain. Here’s just a tip you should know about the .AddIn file that Visual Studio generates for you.
The path you provide to the add-in assembly .dll should be relative to the location of the .AddIn file itself. Absolute paths do not work. If you try using one, you get an unhelpful error dialog that mentions error code 0x80004005.
Hopefully we can get some more useful error messages in future versions of Visual Studio.