Software Update won't connect - "Network Problems"

Mac OS 10.7.2 - 2.4 Ghz Intel Core 2 Duo - 8Gb 1067 MHz DDR3 Memory

I've had this problem for a while.

I try to run Software Update logged in as myself, and I'm the Admin, and I get the above message.

(The internet connection (ADSL2+) is up and running OK).

The only "fix" I could find in the discussion groups; (as it seems I'm not the only person to whom this is happening); was to create a new Admin Account and run Sofftware Update with that.

This worked a few times. Now it doesn't. I get the exact same message.

I tried deleting the old extra admin account and creating a brand new one; but I just get the same message.

What is going on; and please; how do I fix it?

Thanks all.

Robert.