i followed instruction on this page http://www.bdcsoftware.com/googlevoice-for-s60/

Installation

1. Download and install the PyS60 1.9.7 runtime
2. For 3rd Edition phones (N95, E71, E75 etc.): download and install ssl_nokia_1_5_7.SIS
3. Download and install GoogleVoiceForS60_0.7.24_merged.sis
4. Reboot the phone.

Everytime i start the program I get an error "An error occured. Details have been logged"

I don't know where the details are logged.

Anyway, the next screen shows my contact list. If i try to call anyone on the list I get the same message "An error occured. Details have been logged"

==================Also can i get a clarification----------------

Under options: there are 3 fields

User Name:
Password:
Handset Number:

What exactly go into these? I have tried my gmail username with and without the email address.
Under headset number, I have tried both google voice number and my gizmo phone number.