The ethernet cable from one Access Point needs to be connected to one of the 4 ethernet ports in your DG834g router rather then any other computer?
Unless you wanted to have a wireless connection between your router and an Access point?
And really grasping at straws now, maybe thats why 2 Access Points? Even though you could get the reach to your summer house by swapping the Access point's aerial from an omni directional to a uni-directional or even hyperbolic reflector type?
Using MIMO, I've achieved coverage throughout the whole house and right out to the end of my garden as the router is sited in my conservatory.