If you find that the modem is disconnecting or you are having trouble getting a connection then try selecting 3G only or GPRS only.
Below is a guide of how to do this on the E169, E172 and E220 Modems. (Please note that your modem must not be connected to the internet at the time or you will be unable to make these changes)
Vodafone Mobile Broadband E169 Stick Modem
To change between GPRS and 3G networks:
Vodafone Mobile Broadband E172 Stick Modem
To change between GPRS and 3G networks
(This software version only displays the options: 3G only, 2G only and 3G preferred)
Vodafone Mobile Broadband E220 Stick Modem
To change between GPRS and 3G networks
If you are going to be using the modem in one location we advise using the options labelled 3G only or GPRS only as these will supply a more stable connection in areas with weaker signal. The preferred options can cause the modem to move between GPRS and 3G services if coverage is sparse, which can cause pages to stop loading correctly.