Hi Folks -- I didn't realize we had a non-iPhone Mac help group here This is awesome.
Anyway, I have a new 24" iMac, stock machine (2.8Gig, 2Gigs ram, 320Gig HD). No mods. I have wifi in my house (Linksys WRGT with DDWRT), working seamlessly with:
Just got a new iMac 24" and it had airport connectivity issues when I first booted it up. I'd get full signal strength upon start up, but within 1 minute of firing up Safari, it'd go down to 2 bars, and basically stall. The 24" is only 15 feet from the wifi, and is sitting where the 20" iMac used to be - so no interference.
It came with 10.5.2 -- I couldn't update, 'cuz I'd lose my connection -- so I d/l'ed 10.5.4 on my other machine and transferred via USB key. Updated, and voila, it fixed the problem. Perfect connectivity.
1 week later (this morning), it had the same problem again. I brought my MBP to the same desk, right beside the 24", and no problems. I logged into the DDWRT and the signal strength to the 24" was fine. Yet still had intermittent signal problems. Argh.
1 hour later, it spontaneously was working fine again.
I've google'd and searched the apple support sites, and nada. It's only this machine -- the rest are fine. Actually, this machine is fine too, now.