When you are tracking down handle or other leaks you usually need to resort to Windbg which is a great tool for unmanaged code but not so much for managed code because the usual stuff like !htrace only get the unmanaged call stack. For managed code this approach breaks because you will not see which managed callers did allocate or free a handle. Other Windbg approaches like putting a breakpoint and then print out the handle and the call stack at the allocate/free methods work, but for heavily called ......