There was a similar problem some time ago, and was resolved with alloca. I think it's a better solution to use the stack instead of the heap...
Actually, I looked into this and alloca is not standard C++ since it can create problems for the exception handling (although it compiles fine with Visual C). This is probably why there have been compilation problems on some platforms (see http://mail.cs.uiuc.edu/pipermail/llvmdev/2004-September/001992.html) -- A better alternative is maybe to use the std::vector instead of a VLA.
m.