This is not entirely Quake 3 related however the issues were hugely hi-lighted in Quake 3 so I thought I'd post my experiences here.
Before I start, everyone's setup is different so I make no disclaimer that you would experience the same issues I have or indeed that my resolution would work for you either. I'm simply stating my experience so that you may benefit from my hind-sight.
Ok all that aside let's begin. I recently upgraded my network. The original setup ....
Belkin Wireless G 4 port hub
2 PC's wired connections
2 laptops wireless
1 Wired Network Printer (has it's own network port, so not directly connected to any pc).
Upgraded Network .....
Belkin Wireless N1 Router
Belkin G Wireless Print Server connected to the Network Printer
2 PC's using Belkin Wireless N1 USB Adaptors
2 laptops using their own internal cards
And this is where the issues started .
1) Print Server .. It kept dropping the connection ... Also to print you have to use the Belkin print server software to connect to the print before hand and then disconnect after printing to allow someone else to connect to the printer. What a real bind

2) 2 PC's with the Belkin Wireless G N1 USB Adaptors. Wow they worked great .. good range etc .. 300 Mbps connection .... blah blah ...
And that's where it all went pearshape. I fired up Q3 and once in a map I would get for want of a better word sound and frame stutter (connection was fine) ... even offline in single player.
Unplugged the wireless card .. bingo everything ok again ... I spent ages with Belkin support to no avail and after a lot of surfing realised many others were experiencing the same thing or similiar things to do with stuttering with this adaptor.
In the end I took it all back and have bought instead a Netgear RangeMax router (not the new N one) and two Netgear 108 USB adaptors for the PC's ... Network printer is wired into the Router.
The range is excellent and the connection is nice and stable and I've just played RA3 online with no loss of connection or any stuttering at all.
Anyways I hope people find this informative and take from it what you will.
I just spoke to a friend on line and he is using linksys gear so as a recommendation from me ... Linksys or Netgear seem to be a safe bet.
FoRa!