I posted this issue on the Haxe Google Group and here's "the official answer" from Hugh, the creator of hxcpp:
Hi, There is a bug in the 3.0 HXCPP version that prevents the correct stack dump in debug mode in this case. This is fixed in the SVN version. You can also attach visual studio and put a function break point in "hx::CriticalError" and examine the stack there.
Hugh
The next version of hxcpp will have this issue fixed.