Hi Andrew,
Glad you got it fixed :)
Just to make things clear - mstest cannot run in 64 bit context without any relation to Typemock. The mstest.exe binary is built as 32 bit binary and hence will not run in 64 bit.
You can check that by using the corflags.exe utility from visual studio command line:
corflags "c:Program Files (x86)Microsoft Visual Studio 9.0Common7IDEMSTest.exe"
You'll get the output:
Version : v2.0.50727
CLR Header: 2.5
PE : PE32
CorFlags : 11
ILONLY : 1
32BIT : 1 <== This tells us the executable is built as 32 bit.
Signed : 1
My guess is that the code you want to test is still running in 32 bit.