G5 Dual - DVD Reader has gone very very slow after Leopard

Question

After 1 Migrate install and 1 clean install, I notice that reinstalling apps is taking 4/5 times as long as they should it's as if my DVD Reader has gone very very slow. I thought at first it was the migration that had caused FCPS2 to reinstall slow.
(Sony DVD RW AW-G170A 4 months old) on G5 Dual 2's)
FCPS2 wanted 19-hrs to install, I waited 6 hrs and then gave up. Luckily or unluckily as the case may be I used the time install Leo on my other Macs.
In the end I have installed Apps over the Firewire network connected to my other G5 Dual with the stock DVD drive, they are installing fast now.

Answer 1

Some more info about my setup:
*Simultaneous Dual band AEBS:*
Radio Mode: 802.11n only (5 GHz) - 802.11b/g
Radio Channel Selection: Manual - 161 (5GHz), 6(2.4GHz)
*Airport Express:*
Wireless mode: Extend a wireless network
Allow wireless clients checked under the name of the network (same as for AEBS).
Both are WPA/WPA2 Personal security. And both the routers were upgraded to 7.4.2 firmware this morning with the hope that it will help.
*N Devices (both working fine):*
Apple TV 40GB
2009 Model Mac Mini upgraded to Snow Leopard - working perfectly.
*G Devices:*
Thinkpad running WinXP
Dell Laptop running WinXP
Acer Netbook running WinXP
iPod Touch
iPhone 3G
Linksys webcam
_All of the above are working fine_.
+2008 model Mac mini -+ upgrade to Snow Leopard shows extremely slow wifi connection that it is unusable. It takes 20min to load apple homepage. When I boot from the clone of my Leopard lying on my external drive, it works perfectly.
I compared the settings between all the tabs of Network-->Airport-->Advanced and they are identical between Snow Leopard and Leopard mode except that SL doesn't have the "Apple Talk" tab.
Appreciate any help to debug this.