Intel Mac :: Everything Works Except It Won't Load Web Pages Or Connect To ITunes Store, App Store Etc?

On 6 th April my BT homehub2 updated it's firmware and that's when the problems started. Broadband went down completely and powerlineadapters adapters for bt vision fried. After 2 telephone support calls we eventually got the home hub reset and connected to broadband. Bt supplied two new powerlineadapters and bt vision is now working. Laptop, iPhones and iPad (and bt vision) all connect fine and work completely well. 

My iMac running OS X 10.7.3, appears to work in that it connects no problem to home hub and when you run diagnostics it says your Internet connection appears to be working normally... However I cannot get a web page to load - I have tried chrome, Firefox and safari. The bizarre thing is using Outlook I can send and receive email, also my apple devices are still syncing via the iCloud - that would suggest that the iMac is indeed connecting wirelessly to the router and sending and receiving data - just no web pages at all - also it can't connect to things like iTunes store or apples app store... Everything was working fine until the firmware update!  

Also may/may not be related but when I log in now I always have to manually connect to router, it always connects fine but it used to do it automatically, also recently upgraded to Lion and I have my doubts there too? 

Info:
iMac, Mac OS X (10.7.3)