I faced same problem as you described. Then I disabled and enabled Change Tracking, installed latest service pack with no success, Nothing was the solution for my case.

Then I followed below way. It solved the problem.

1.Put database single user mode.

2.Create a DAC Connection to database. For DAC info click here.

3.Run this : DBCC CHECKTABLE("sys.syscommittab", REPAIR_REBUILD)

4.Put database multi user mode.