Possible Firewall or Proxy Issue?

A few weeks ago, I restored my computer to the factory image. I'm running Windows Vista Ultimate 32bit and haven't installed any service packs yet. About a week ago, however, I was randomly prompted to validate Windows again, even though I had (obviously) done it when I first restored my computer. I'm thinking this is when the problems started, but I don't really know how to pinpoint it, as I've been noticing new issues every couple of days.

Either way, I now cannot do any of the following:

• install any updates with Windows Update
• update antivirus definitions
• connect to Windows Live Messenger
• connect to Steam
• load AIM Lifestream
• load pages in IE 8 or Chrome
• use anything but the "basic uploader" for pictures on Facebook or attachments on Gmail using Firefox

I'm sure there's more to add to this list, but I'm still discovering them as I go along. But I'm thinking it's a firewall or proxy issue, although Windows Firewall is disabled, and I don't know what else would be enabled. There is the possibility of it being a virus, though, right? Any suggestions for what steps I could take to figure this out?

Support for "Vista without service packs" ended on April 13, 2010. You should have put in the service packs. Good possibility of a virus because "Microsoft" won't security update you...

End of support for Vista without service packs. - Vista Forums

So would it be an option to install Service Pack 1 and then go from there, or should I just start over by reverting back to the factory image and getting SP1 installed ASAP before this happens again?

What exactly are your error codes ? I could tell more with the error codes. Your missing loads of repairs and software downloads, security fixes etc. I'm thinking that is probably the problem. Perhaps it would be better to do a clean install after a scan for virus. Download your service packs and take from there.