WUS: Updates not downloading

Hi,

After a few days of fluffing around, I've finally managed to get WUS working
so much as clients showing up in the WUS console, however, WUS is unable to
download updates from Microsoft. When I approve an update, a red cross
appears next to it.

I understand that ports 80 and 443 need to open in a firewall environment
for the updates to download. I believe I have done this correctly.

Where are these sorts of errors logged to?

Thank you,
Dennis.