Overloading mess: No matching function for call

Hi.
I wrote a code similar to this one, for a wrapper application that I
needed:

#include <iostream>

using namespace std;

class Client
{
public:
    void setEndpoint(const string& s) throw() { a_endpoint = s;
setEndpoint(); }

protected:
    virtual void setEndpoint() throw() = 0;

    string a_endpoint;
};

class NotifyClient : public Client
{
public:
    const char* endpoint;

private:
    void setEndpoint() throw() { endpoint = a_endpoint.c_str(); }
};

int main()
{
    NotifyClient client;
    string url("http://www.google.com");
    client.setEndpoint( url );

    return 0;
}

But I'm getting this compile error with g++:

inheritanceTopic.cc:30: error: no matching function for call to
`NotifyClient::setEndpoint(std::string&)'
inheritanceTopic.cc:22: note: candidates are: virtual void
NotifyClient::setEndpoint()

If I change the line,

    client.setEndpoint( url );

by

    client.Client::setEndpoint( url );

it works.

I'm wondering why is it. I guess it has something to do with function
overloading and the compiler, because if I change names, it works too.

Can anyone give me a better explanation?
I would like to use the same name in the functions, but I don't like
the style of:

    client.Client::setEndpoint( url );

pretty ugly....

Thanks in advance,
Tomas.