There appears to be a discrepancy between the solution's source control information about some project(s) and the information ...

There appears to be a discrepancy between the solution's source control information about some project(s) and the information in the project file(s).

To resolve this discrepancy it will be necessary to check out the project file(s) and update them. If the check out fails, however, and the solution is closed without saving, you will see this warning again the next time you open the solution.