Multi-argument template functions, overloading and ambiguity errors.

Question

Lets say I'm writing a some kind of conversion operator, and I want to use it like that:

SomeType a;
AnotherType b = conv<AnotherType>(a);

First, I write the base (default) function:

template <typename T, typename U>
inline T conv(const U& a)
{
    return T(a);
}

Full specialization (or a non-template overload) is not a problem, however, when I want to do something like that:

template <typename T>
inline Point<T> conv(const Ipoint& p)
{
    return Point<T>(p.x, p.y);
}

I can't write any more conversion functions from the Ipoint (to the FunkyPoint< T > for example) due to ambiguity, and I end up with an awkward usage:

Ipoint a;
Point<double> b = conv<double>(a); //ugly!
//Point<double> b = conv<Point<double> >(a); //I want that, but it (obviously) does not compile.

Is there any way of doing it nicely?