Wireless working fine, LAN cutting out constantly

Hey guys, here's my problem.

We have two PCs in our house, let's call them PC1 and PC2.

PC1 is a 6-year-old store bought machine running on a wired connection sitting no less than 1meter away from the router.
PC2 is a less than 9 month old self built gaming rig running on a Wireless connection in a different part of the house.

PC2 works perfectly all the time, so no complaints there, however PC1 only works properly when PC2 is not connected to the gateway, the connection on PC1 will cut out every 5-20 mins when it is, can anyone here suggest why this happens and anything I can do to solve it? Thanks.

I'd draw it out like this, I suppose.

PC1---(Wired)--- Router - - - (Wireless) - - - PC2
Netgear WNR834M
|
|
Modem
(Whichever one you get from Virgin Media fibre-optic cable connection upto 20MB)

Both machines are getting their own IP address and I've done several soft(power) and hard(factory) resets on the setup

I've changed the cable and the port (that was the first thing I thought of myself) and I've tried my spare laptop on wired and wireless connections and my PS3 on wired and wireless connections to the router and neither have the same problem except when wired.

Alright, thanks for your help.