Type of unsigned long is different from uint32_t and uint64_t on Windows (VS2010)

On Visual Studio 2010 under Windows 7, 32bit, unsigned long seems to be a distinct type from both uint32_t and uint64_t. See the following test program:

#include <stdint.h>
#include <stdio.h>

template<class T, class U>
struct is_same_type
{
    static const bool value = false;
};
template<class T>
struct is_same_type<T, T>
{
    static const bool value = true;
};

#define TO_STRING(arg)        TO_STRING_IMPL(arg)
#define TO_STRING_IMPL(arg)   #arg

#define PRINT_SAME_TYPE(type1, type2) printf("%s (size=%d) %s %s (size=%d)\n", \
    TO_STRING(type1), int(sizeof(type1)), \
    is_same_type<type1, type2>::value ? "==" : "!=", \
    TO_STRING(type2), int(sizeof(type2)))


int main(int /*argc*/, const char* /*argv*/[])
{
    PRINT_SAME_TYPE(uint32_t, unsigned long);
    PRINT_SAME_TYPE(uint64_t, unsigned long);
    return 0;
}

I'd expect it to print either

uint32_t (size=4) != unsigned long (size=8)
uint64_t (size=8) == unsigned long (size=8)

(which I get on x86_64 Linux) or

uint32_t (size=4) == unsigned long (size=4)
uint64_t (size=8) != unsigned long (size=4)

assuming of course that long is not longer than 64bits.

On Windows however, I get the baffling

uint32_t (size=4) != unsigned long (size=4)
uint64_t (size=8) != unsigned long (size=4)

which means that there are two distinct 32bit unsigned types. Is this allowed by the C++ standard? Or is this a bug in the Visual C++ compiler?