NullReferenceException in TypeMock.dll

I just downloaded a trial and tried to create a new unit test using it, but when I run the test I get a NullReferenceException in the constructor of the unit test *class* itself:

>   TypeMock.dll!e4.e4() + 0x65 bytes   
    [Native to Managed Transition]   
    [Managed to Native Transition]   
    TypeMock.dll!TypeMock.MockManager.f(System.Type A_0 = {Name = "P2_Session_Tests" FullName = "UnitTests.P2_Session_Tests"}) + 0x63 bytes   
    TypeMock.dll!ai.g(System.Type A_0 = {Name = "P2_Session_Tests" FullName = "UnitTests.P2_Session_Tests"}) + 0x2f bytes   
    TypeMock.dll!TypeMock.MockManager.IsTypeMocked(System.Type type = {Name = "P2_Session_Tests" FullName = "UnitTests.P2_Session_Tests"}) + 0x3c bytes   
    TypeMock.dll!TypeMock.MockManager.GetMocks(System.Type type = {Name = "P2_Session_Tests" FullName = "UnitTests.P2_Session_Tests"}) + 0x34 bytes   
    TypeMock.dll!TypeMock.MockManager.c(object A_0 = {UnitTests.P2_Session_Tests}) + 0x7d bytes   
    TypeMock.dll!TypeMock.MockManager.a(object A_0 = {UnitTests.P2_Session_Tests}) + 0x3e bytes   
    TypeMock.dll!TypeMock.MockManager.b(object A_0 = {UnitTests.P2_Session_Tests}) + 0x4d bytes   
    TypeMock.dll!TypeMock.MockManager.a(string A_0 = "UnitTests.P2_Session_Tests", string A_1 = ".ctor", object A_2 = {UnitTests.P2_Session_Tests}, object A_3 = null, bool A_4 = true, object[] A_5 = {object[0]}) + 0x26d bytes   
    TypeMock.dll!TypeMock.InternalMockManager.getReturn(object that = {UnitTests.P2_Session_Tests}, string typeName = "UnitTests.P2_Session_Tests", string methodName = ".ctor", object methodParameters = null, bool isInjected = true) + 0x60 bytes   
    UnitTests.dll!UnitTests.P2_Session_Tests.P2_Session_Tests() + 0x51 bytes   

For reference in the above call stack, "P2_Session_Tests" is the class name.

I couldn't reproduce this in a brand new project with no references, so the only thing that I could think of was that maybe it's something to do with one of my references. However, I commented out all code from my unit test project, except for the class definition and a single method and even removed all non-framework (or Typemock) references, but I still get the same error.