Just had this one creep up on me after reinstalling XP:
[Error number: 0x80072F8F]
Your computer’s date and time appear to be out of sync with an update certificate. To fix this:
1. In the Control Panel, open date and Time Properties
2. Ensure that the date and time are correct.
Read more about steps you can take to resolve this problems (error number 0x80072F8F) yourself.
After mucho searching, newsgroups, etc. I found what worked for me so I had to blog about it because it took forever to find! You will kick yourself for not thinking of this one. Check your BIOS clock!!!!! Mine said 2002…only 4 years ago! Apparently the SSL Certificate validation uses an API call or something that ends up checking your BIOS clock and not your Windows clock. I hope this saves someone out there a couple of hours and some gray hairs. Good Luck!