iPhone 4.3.1 update issues-Wifi

Hi all
Updated my iPhone 4 to 4.3.1 last week, and since this morning when i arrived at work, my Wifi wont automatically connect. I am connected to the network, but it just has the E in the top left. If i turn 3G on, the Wifi symbol appears briefly and then goes away again. I havent tried it at home as i only noticed when i got to work this morning.
Anyone else having similar issues? I have hard reset, re-booted and reset my network and all my settings. Still no luck.
Any help appreciated.
Macbook Mac OS X (10.5.8) iPhone 4 16GB