VC6 vs VC7 function overloading

[JMon]

I have a string class that overloads the const char* operator as
follows:

mystring::operator const char* () const
{
return this->c_str();
}

I have another class the overloads one of is functions as follows:

void myclass::func(mystring& x)
{
// do something
}
void myclass::func(const char* x)
{
func(mystring(x));
}

With VC6 the 2nd func() calls the first func(), but with VC7 it calls
itself. Any ideas why this is and which compiler is correct?