Symptom
The modem settings located within the network system preferences, has two sets of modem scripts for the internal modem. They are:
1. "Apple Internal"
Apple Internal 56K Modem (v.34)
Apple Internal 56K Modem (v.90)
2. "Nifty - Apple Internal"
Nifty - Apple Internal 56K Modem (v.34)
Nifty - Apple Internal 56K Modem (v.90)
Solution
The "Nifty" scripts, installed by default, are localized for Japan. Only use these if you are in Japan.