iPhone 4 Hotmail Exchange

Hi,
I just setup hotmail on my phone, using exchange. I used ALL the correct details, and it verifies my account, and does the first sync, but when I go to view the mail, I get Cannot connect to server (or something along those lines.) My friend has the exact same phone on the same plan, and it works for him fine.
Any ideas why it doesnt work for me?
HP Compaq nx8420 Windows 7