Updating to the latest firmware and Vodafone Mobile Broadband software did not solve the issue for me. However, I found the following solution.
1) Install the latest Vodafone Mobile Broadband (VMB).
2) Open VMB, go to its Preferences. On the "Start & Quit" tab, use the following:
- Do not start this application (when OS X starts up)
- Untick "Start this application when a mobile device is plugged in or switched on"
This ensures that VMB does never start automatically.
3) Now, in System Preferences, in the Network section there should be a Vodafone K3765 modem. Set it to use the following (using an administrator account):
- telephone number *99#
- account name vodafone
- password vodafone
- tick Show modem status in menu bar
- Apply
4) Now, from the modem icon in the menu bar you can connect and disconnect.
The VMB software is never started. You cannot use it to monitor your usage. However, you can start and stop the modem using standard Apple controls, and the connection will not disconnect after a few seconds.
It may not be ideal but this works realiably for me; the VMB software does not.