Hi!
yes i think... windows wants to check the serial keys -.-
Ca 3 weeks ago on M$ Windows Update Site you will be asked if you want to send your Serials Key and data... since 1 week you will not be asked... they just do it and u have to look

So now M$ may have got a new "SerialKey-Check" and to force the people to make update, they published the following vulns as critical:
# MS05-038 <#038>: Cumulative Security Update for Internet Explorer
# MS05-039 <#039>: Vulnerability in Plug and Play Could Allow Remote code
Execution and Elevation of Privilege
# MS05-040 <#040>: Vulnerability in Telephony Service Could Allow Remote
Code Execution
# MS05-041 <#041>: Vulnerability in Remote Desktop Protocol Could Allow
Denial of Service
# MS05-042 <#042>: Vulnerability in Kerberos Could Allow Denial of
Service, Information Disclosure, and Spoofing
# MS05-043 <#043>: Vulnerability in Print Spooler Service could Allow
Remote Code Execution
So all People are realy asked to update their systems and send the Serial Keys to M$... thats my theorie

In your case, M$ force the update harder, due install it secretly...
cheers
digital-flow