Why can I browse with Firefox but not with Safari or Chrome?
I can't be 100% sure which of these resolved the issue but i took these steps and everything is now working (touch wood):


Terminal

sudo mv ~/Library/Keychains/login.keychain ~/Library/Keychains/login.keychain.bak
sudo mv /Library/Keychains/System.keychain /Library/Keychains/System.keychain.bak

Reboot
I'd now lost network connectivity and wifi wouldn't connect- i think this is because the wireless key is stored in the keychain which i'd "deleted". I managed to resolve this by going to network preferences, wifi, assist-me and stepping through the wizard.
Lastly i ran software update and upgraded to 10.7.3


Voila