I am currently using TFS with Visual Studio 2010 Ultimate and getting this error when I try to open up my solution:
The associated source control plug-in is no
For anyone (like me) who was looking for an answer to this . . .
I had the same issue, and I came across a couple of things that might be helpful.
First, I found this link on MSDN.
Second, I opened a solution in VS2010 (not my project), and got the same message. It gave me the options to either temporarily work with the solution uncontrolled, or to permanently remove source control association bindings. I went with the latter (again, this was a project I inherited, not one I built), and it seems to be okay.
To anyone who finds this, I hope this helps!