We've owned the GC for three weeks and have not been able to "register" our VIN with the site.
I registered upon delivery of my vehicle at the end of Feb. and was able to use this part of the site for several months. Then all of a sudden clicking the sign in button would actually close my Internet Explorer. I was not too concerned because I had XP and was going to eventually get 7. I now have had 7 for a week and while it does not close, I get the "service" message.