Can't share a dial up Internet connection with an iPod Touch

Hi there

My cousin have got a MacBook Pro and an iPod Touch; he wants to share his (dial up) Internet connection on his MacBook Pro with the iPod Touch, but we failed to do so everytime. At first I thought there was something wrong with the setting, so I bought the iPod Touch home and tried it on my Alu iMac. Everything worked fine at my place. I can surf the Internet thought my iMac's dial up connection. I even reinstall the system for MacBook Pro, but nothing has changed. I know its not the iPod Touch's problem because it works fine with my iMac. Just wondering is anyone getting the same problem? Here is the specs for my cousin's MacBook Pro:

Apple MacBook Pro 15" 2.2GHz
2.2GHz Intel Core 2 Duo
2GB memory
120GB hard drive
8x double-layer SuperDrive
NVIDIA GeForce 8600M GT graphics with 128MB SDRAM
Glossy Screen

Here is the steps I take to share the Internet connection:
1. Connection to the Internet using Apple's USB modem
2. Go to: System Preferences -> Sharing -> share my connection from External Modem via Airport
3. Check the checkbox for Internet Sharing.

I did exactly the same thing on the iMac and MacBook Pro. The Internet sharing works fine on my iMac, but for some reason, the MacBook Pro just can't seem to share its Internet Connection.

Later on I tried to share the Internet connection on the MacBook Pro and ask my iMac to connection to the network...everything works fine...I can surf the Internet from my iMac via the MacBook Pro's USB External Modem...but the iPod Touch still refuse to open any webpages:(

Also I think I've found a bug in the system...there are two USB ports on the MBP, one on the left and one on the right, if I connection the USB modem to the one on the right, connection to the Internet and start sharing my Internet connection, the MacBook Pro will crash everytime. I have updated the Mac OS X Leopard to 10.5.1 and did all the updates. Not sure whether others are having the same problem, but this "trick" crash the MBP everytime.

Thanks for reading my post...it would be great if I can get some help on this issue. Thanks again.

+p.s. I know its pretty crazy to share a dial up connection with other computers...but for various reason, we have to use dial up for now.+