There could just be a nearby interference source that is disrupting his connection. Look for stuff like wireless speakers, headphones, telephones, microwaves, and the like anywhere around his computer location. Could also just be it is in a bad location for reception of the radio signal due to the walls, floors, etc. You can test that out by moving his computer to a different area of his room of using a wireless adapter with a removable antenna that you extend to a new location with a cable.
Also he might be getting interference from a nearby network at a neighbor's house and changing radio channels could help.