wireless network "frequent transitions"?

[Chris Murphy]

New laptop with 10.5.2 shipping on it seems to have a lot of network  
anomalies compared to a Powerbook with 10.4.11 which has no such  
anomalies in the same environment (and location). Symptoms are high  
latency (slow to establish connection) to servers, iChat being  
"chatty" with connection status, email that occasionally won't send.  
The only clue at the time of these events are numerous entries like  
the following in Console:

May 25 16:50:04 colormac kernel[0]: AirPort: Link Up on en1
May 25 16:50:04 colormac mDNSResponder[22]: Note: Frequent transitions  
for interface en1 (192.168.1.103); network traffic reduction measures  
in effect
May 25 16:50:12 colormac iChatAgent[10274]: WARNING: SocketStream:  
CFStream error 1/57 occurred on input stream
May 25 16:50:12 colormac iChatAgent[10274]: WARNING: XMLStream:  
CFStream error 1/57 occurred on input
May 25 16:50:12 colormac iChatAgent[10274]: WARNING: JConnection:  
Error: Could not connect to server: talk.l.google.com, type=0, code=57
May 25 16:50:51 colormac GoogleUpdateChecker[14283]: LCC Scroll  
Enhancer loaded
May 25 16:50:57 colormac mDNSResponder[22]: Note: Frequent transitions  
for interface en1 (FE80:0000:0000:0000:021E:C2FF:FEB9:8B73); network  
traffic reduction measures in effect
May 25 16:51:01 colormac mDNSResponder[22]: Note: Frequent transitions  
for interface en1 (FE80:0000:0000:0000:021E:C2FF:FEB9:8B73); network  
traffic reduction measures in effect


Flummoxed. This is intermittent, in that this goes on for maybe an  
hour then stops for quite a while. So far I haven't determined a  
pattern, but it doesn't happen all the time.

Separately, but perhaps related or perhaps not, is something very  
different about this new hardware compared to previous experience is  
that the airport signal indicator on the menu bar is either at maximum  
or it will not find/connect to the wireless network. If connected, it  
always indicates maximum signal. Otherwise it is disconnected from the  
network.

Suggestions?

Chris Murphy