Trouble Using University's remote client AV

I've downloaded the Sophos client from my University's IS portal and installed it on my Mac. The guide on the Uni's website says the primary server should already be filled in but mine wasn't so I entered it manually by looking at their screenshot. When I select update now it shows me update is in progress by the loading bar moving and the number of files installed keeps increasing. Once the loading bar reached 100% I get told update failed!!? I've tried installing it twice and updating several times with the same outcome...

What I am not understanding is that I installed it on my Windows machine and updated no problem (although the update URL was of course different for Windows platform)

I'm running OS X 10.6.3 and Windows 7. The link to download the Mac client says 10.2+(inc. Mac for intel) so it shouldn't be a problem as the link to download the Windows version only mentions up to Vista yet as I said installed fine on my Windows 7.

Is anyone able to help?

Thanks