[andrewas]

As lennon said, this dosent look much like a server side problem. A cookie glitch from server side woudnt appear between software upgrades like this.

Although how a cookie glitch on the client side can begin affecting multiple people including the webmaster at the same time is puzzling.

Another theory is that something on the web, new spyware perhaps, is glitching cookies on a wider scale. I run adaware regularly, but it isnt updated as often as a true AV product would be, so a new spyware could get around a fair bit before it was detected.