If the problem does turn out to be the wireless, you could look into getting these.
http://www.dabs.com/products/devolo-dlan-200-aveasy-adapter---homeplug-av--powerline-5084.html
In a nutshell.
You plug one in to the nearest powerpoint to the router and connect it to the router via a network lead.
You take the second one and plug it into the nearest powerpoint to where you want to use the computer and again connect the computer to this adapter via a network lead.
I won't go into too much detail but basically they turn your home electricity wiring into a wired network.
So with these you would have the freedom of wireless (almost) but the stability of a wired network.
So first of all we need to see if it is infact your wireless causing the problem (In my opinion its the most likely cause)