We restored the firewall default settings, after checking and double-checking that there was no third-party software on the system using the Microsoft Cleanup utility thingy...incidentally, I was unable to download it until I disabled the firewall, and then it downloaded fine. Once the firewall was reset to default settings. I attempted to update MSE...it timed out with a failed connection. I attempted to run Windows Update, with the same result.
I disabled the firewall and was able to update both programmes.
The computer is only three weeks old; it came with a Norton Trial version, but we wiped the hard drive completely and created two, brand new partitions before installing Windows 7. I can find no trace of anything that was loaded onto the computer prior to the wipe.
I don't believe it is a router problem as we have another computer which allows us to update Windows, download programmes etc with no issues at all.
We were directed to two separated sites (by Microsoft support after logging an issue) to download msicuu2.exe to clean up the system and then conduct a manual update from this site: How to obtain the latest version of the Windows Update Agent to help manage updates on a computer
This computer blocked access to both these sites and I was unable to download the first program, or get access to the second program unless the firewall was disabled. Both sites worked on our other computer, hence my comment that it doesn't seem to be a router problem.