Test Navigator stuck loading solution

Using VS2013, and typeMock 7.5.6.1 (C#). Opening an existing project the unit tests run fine in mstest but the typeMock test navigator shows "Loading Solution" and hover on any of the shields in the unit tests shows "Analyzing in Progress" but it never completes and the tests can't be run from TypeMock. Several other legacy projects worked fine - am I missing a setting?