Dell Latitude 620 battery life

I have a 4 month old Latitude 620 which was giving me 3 to 4 hours battery life that was great for working on the long Australian transcontinental flights.

Trouble is that my battery life has just dropped to about 1.5 hours - which is not so great.

The only change I've made is to install a Telstra Next G wireless broadband card with a HSPDA driver.

Can anyone suggest things to check to eliminate what is killing my battery?

I've checked the power management settings. They are the same as before.

The Power Management properties of 2 of the 3 network adapters are set to "Allow the computer to turn off this device to save power". The third Network adapter device, Globe trotter HSDPA Network Card, does not give you that option.

The only thing I have not tried yet is disabling all the network adapter drivers (when not connected to the network) to see if one of them is killing my battery.

I borrowed another battery tonight and got even less life out of it - so the battery is not the problem. Something in my Dell is sucking the life out of the battery.

Any comments will be most appreciated.