Blackberry Bold does not update.

I have a Blackberry Bold, and wanted to respond to this post as I have similar issues. My background fyi
- I have a UK Vodafone sim card, and bought my bb bold from Vodafone in the UK
- I have just come back from the USA, where I had an AT&T sim card in my (now) unlocked Vodafone BB
- TT worked like a charm in the US
- Now I am back in the UK, with my Voda sim card, TT does not update the twitterstream of those I follow, nor submit a tweet
- *However*, it _does_ pull down the public timeline and I have checked that the correct credentials are entered (therefore I'm assuming it's not a comms problem)
- I am using the default connection option in general settings
- When I switch off the Voda connection, TT does not work with my Wifi network, even though browser works without problem
- I have two Twitter accounts, and Twitterberry works without problem using my other account

So, I'm a bit stumped (and sad)