Ok, may have some help for you on this one.
I had similar problems recently, slow connections, couldn't use VNC anymore..thought it was my Dell Mini, I was using the Ericsson/Dell Wireless Connection Manager, but I think I've pinned it down.
Vodafone must have made some changes at their end. The Ericsson/Dell Wireless Connection Manager uses an NDIS connection when you hit Connect, in other words it sets up a Mobile LAN Connection, you will see it when you connect, if you go into Network Connections. This is hugely useful, since it allows the laptop to switch between the best connection seamlessly, either your 3G or your WIFI if it is connected. Until recently, this worked brilliantly. When my problems arose, I checked the Vodafone Mobile Connect Software, and noticed it operates in a completely different way - it uses a Dial Up (DUN) connection to Connect.
So I tried setting up a DialUp Connection seperately with the Ericsson/Dell Wireless Connection Manager installed. It works flawlessly but sadly you have to got to Network Connections and hit the DialUp Connection, you cant simply hit "Connect" on the Ericsson/Dell Wireless Connection Manager Window. Hopeless, since this renders the Ericsson/Dell Wireless Connection Manager completely useless, and no notification of speed or usage - except that of course you can use other network SIM cards.
So you basically have two options now...use the Vodafone Mobile Connect Software, OR use the Ericsson/Dell Wireless Connection Manager and setup/connect with Dial Up Networking.
I would love to get the NDIS/WWAN (Mobile LAN Connection) option to work since it is fantastic for switching between the best connection, so anyone with info about how we can get this working properly again, would appreciate.
Here is a link for setting up a Dialup Connection with the Ericsson Wireless Connection Manager, and explanation of NDIS and DUN. http://www.sonyericsson.com/cws/downloa ... R1a_EN.pdf