it turned out that when I replaced my Linksys 802.11b with
a brand new Motorola 802.11g the problem went away; there is a Radio
Shark on the third floor of City Center that sells them for $70.
Similarly, when I put a $70 Linksys WPC54G (directly supported by Mac
OS X 10.2.8) into my Powerbook to override the builtin (Lucent-made)
Airport card, and switched on "Interference Robustness", I got much
more consistent network access.
I'm still losing network access now and then, and my TCP connections
mysteriously wedge sooner or later, but I'm functional.
I would suspect that most people complaining are using the time-tested
Lucent/Orinoco card, which is now getting a bit old.
It sure makes sense to have a deck of cards available if you really
need the Wi-Fi.
Gruesse, Carsten