UnitTest failing only when all tests get executed at once

I'm currently facing an odd problem when running a Microsoft C++ UnitTest within VS2013.

The test is failing each time I execute Run All tests in the IDE, but when I use Run Selected Tests on the specific one, it succeeds.

What I'm testing for is the usage of my own BinarySearchTree class. In case of failure, the exception code C0000005 gets returned (this may be due to wrong internal linkage of pointers).

So what can be the reason for this?