Some people have reported problems after updating the iPhone to the new 4.2.
The automount doesn't work. You'll receive an error like this:
Unable to mount iPhone_ org.freedesktop.DBus.Error.NoReply DBus error: MESSAGE DID NOT RECEIVE A REPLY (TIMEOUT MESSAGE BY BUS)
This is how to fix it:
Open your terminal and copy/paste the following:
sudo add-apt-repository ppa:pmcenery/ppa sudo apt-get update sudo apt-get dist-upgrade
restart your system and mount your Iphone without problems.