I wanted to create two different Features in Visual Studio 2010: one to deploy a list definition to the Site Collection, and another to deploy an instance of that list to a particular Web. When I created my list definition, Visual Studio asked me if I wanted to create an instance of that list, too. I said I did, and it placed an instance of the list inside my list definition folder in Visual Studio. I then went and created my two Features.
When I activated my list definition Feature, it activated without problem. When it came time to activate the list instance, I got a strange error:
[COMException (0x81072101): <nativehr>0x81072101</nativehr><nativestack></nativestack>Cannot complete this action.
The way I resolved the issue was to simply create separate a separate list instance for my list in the root of project, removing it from within the list definition folder. (A simple solution that took me hours to solve!)