Well, my Mobile Internet showed up automatically when I inserted the Vodafone SIM. Considering that you're having a dataplan active, try the following settings. Also, the settings that are available on the Vodafone page in the link above are for Vodafone LIVE! not for Mobile Internet. What kind of dataplan do you have?

Access point name: internet.vodafone.ro
User name: internet.vodafone.ro
password: vodafone (If I remember correctly)

At the first screen, set Connection name as you wish, it says Mobile Internet for me.

In the advanced settings tab, just check Retrieve IP automatically and DNS automatically.

It should work for Mobile Internet package subscriptions. If you have that 4 EUR Vodafone Live the settings are different. let me know.


EDIT: here are the settings for MOBILE INTERNET:

http://setari-telefoane.vodafone.ro/...rvice=postpaid

and here are the settings for Vodafone LIVE! (Vodafone Internet mobil)
http://setari-telefoane.vodafone.ro/...rvice=postpaid

all you need to set with your N900 are the access point name, username and password:

MOBILE INTERNET:

access point name: internet.vodafone.ro
username: internet.vodafone.ro
pass: vodafone

Voda LIVE:

access point name: live.vodafone.com
username: live
pass: vodafone

the rest should be DHCP. Hope it helps.