Thread: send( accessing beyond buffer?

I've been working on a game.
One of the things the client-side code has to do is send the name of the player to the server. If I type anything that's more than 3 characters for the name ("Dude" for example), I get error box from Windows saying "Run-Time Check Failure #2 - Stack around the variable 'buf' was corrupted."
I did a little research, and this error only happens when an array is getting accessed outside of it's space.
So my question is, why is send( trying to access beyond 'buf'?

Code:

int SockSend(SOCKET *tsock, char* buf, int len)
{
	int nError;

	nError = send(*tsock, buf, len, 0); // Error triggers here; does not stop execution, though
	if(nError == SOCKET_ERROR)
	{
		printf("SockSend: send( failed: %d\n", WSAGetLastError());
		closesocket(*tsock);
		WSACleanup();
		return 0;
	}

	return nError;
}

Where 'buf' would contain "S04Dude" and len is 7.