On site with a customer today, and I have been running into multiple issues with Microsoft Genuine Activation, and it took a while but I have uncovered the fix.

In my case: I'm configuring Windows XP SP3 (so you are running a different OS, your results may vary)

With that being said, XP was throwing up messages about not having a valid OS, and it needing to phone home for updates and Genuine Activation process. The Microsoft Genuine Activation was failiing after repeated attempts and multiple access methods to the internet (LAN, Wireless, Broadband). It kept throwing up a blank page on the site. So from my guestimation the site or something along the lines of there DNS or Time Servers is off, but that will take more research.

To fix the issue:

Change the Windows OS system date to a couple days ago (in my case I changed it from today (Tuesday) to Sunday

I re-opened Windows Update and this time my Windows Genuine Activation COMPLETED SUCCESSFULLY

I'm now successfully activated and able to continue updating my OS. Once you're done updating, be sure to change the system date and time back to the correct settings.

Hope this helps you if you're running into the same type problem!