Pesky Intermittent Wi Fi Connection

Perhaps someone can help me with sporadic intermittent connection issues
Its on an impatient nube relatives computer
Its in an area with a ton of competing signals
On top of that he is up around 10 stories up for excellent reception of any interfering rogue wi fi signals
Only one computer of the 4 seems to have intermittent sporadic connection problems
Its a standard G setup on a standard USRobotics Turbo G router
The wireless router is free , clear and unobstructed
The offending computer is in clear view across a living room about 20 feet away
Various channels have been tried that seemed open
Recently the wireless router was set to automatic and somehow it had settled on the congested channel 6 automatically by itself
Even on relatively open channels 1 and 3 similar results occurred
I have swapped in new computers , and new wireless network cards to no avail
I am using WEP 64 for encryption
I have tried moving the router over a foot or so
The wireless is now set to "g only" as opposed to "mixed " ( B and G)
The SSID is not generic
Its a low case computer I have been using generic Zyadas G USB adapters
Any ideas ? The relative is both a nube and relatively dubious that one computer out of the lot can only have these sporadic connection issues
As I said I have changed the computer and done a number of fresh installs to rule out spyware
Reception is a very wi fi dense area of upscale condos and apartments in a clear view highrise that could get any of a number of rogue signals drift in out the blue
Its difficult working with relatives at the best of times I guess.
Time to shove off and move on , still I do not like to leave open problems dangling
Any ideas would be very much appreciated - lest I be seen as a wireless networking incompetent

 

Install Netstumbler on the suspect PC.
http://www.netstumbler.com/downloads/

See if the signal stays consistent and what other signals are in the area.

 

I would turn off access to any networks beyond the desired one. You can disable any other networks from being in the available list, and specify to connect to one specific network only. Do that.

tom