Do you ever have this exception during the opening of a solution?
Projects have recently been added to this solution. Do you want to get them from source control?
What is this exception saying? In my case it was that, I have created a new project on another computer. Then I checked-in the solution changes without checking-in the changes of the new project. After checking-out the changes on another computer, I got this exception. Now the issue is clear. The solution file has the information about the new project but the new project does not exists on the Team Foundation Server. You can see that the solution file has the information about the new project by opening the Solution Explorer. There should be a project that has a name that contains the description “unavailable”. To resolve the problem, either delete the newly created project or check-in any changes from the computer where you created it.