Yesterday, the hard drive in my 12" PowerBook G4 (purchased in April, 2004) died a horrible, painful death. After doing some testing on the machine (it typically doesn't hold any critical data, so it's an ideal test platform), it failed to reboot. Long story short, the hard drive was dead. Really dead -- Disk Utility told me "This drive has reported a fatal hardware error to Disk Utility. If the drive has not failed completely, back up as much data as you can and then replace it with a working drive." Thankfully, it then mounted in a partially-usable state, and I was able to retrieve the one bit of non-backed up data on the drive (my wife's Palm Pilot contacts, which contained updates she hadn't yet synched back to the Pilot).
After installing a new drive and reinstalling 10.5.2, I set about copying key files and programs back to the machine. However, my AirPort performance was glacially slow: time estimates to copy 70MB of data were in excess of 45 minutes! Some Google searching told me that I was not alone. Apparently this is a pretty big issue for many people on 10.5.2, but it's not universal -- our MacBook Pro, for instance, sees no such slowdowns.
I haven't marked this hint as 10.5 only (as the solution can be implemented on 10.4, too), but it does seem that the problem is limited to those running 10.5.2, and using AirPort on either Intel or PowerPC machines. Read on for the solution...
That linked thread from Apple Discussions contains a potential fix. John Albergo theorized that it might be related to the TCP setting for "delayed_ack", and offered this one-line Terminal solution:
sudo sysctl -w net.inet.tcp.delayed_ack=0
The default setting is three; the above command changes it to zero until the next restart. (For a permanent fix, John linked to this blog post that contains a Startup Item to run the above command at each boot.)
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080305053403936