Grover, your cookie values look like you're not clicking "stay logged in", which is very strange. There are some other cookies (Google Analytics mostly) which are non-session cookies, so I'm not sure why that wouldn't work.
Assuming xenforo isn't in the exclusions, if the checkbox is ticked, the cookie should be created. Perhaps the issue lies with the tick not being recognised?
Have you tried the hard refresh, cache clear, cookie clear etc?
try reinstalling or upgrading chrome. make sure you export your bookmarks via the bookmark manager before you do. Check out chrome 10 beta: http://www.google.com/intl/en/landing/chrome/beta/ - see if this fixes your problems. You say you've tried everything else, if this doesnt work, Idk what will.
I was about to do this... but miraculously today I discovered that the problems has disappeared!
. I am not sure if it's related but next to XenForo.com I had another site where there was a problem: this site gave me a warning that it could not be used (whereas I always used it without any problems), because my browser apparently didn't accept cookies, according to that site. However, my settings in Chrome allowed cookies, naturally. So I had 2 sites giving me 'headaches', including xenforo.com
Now, suddenly both sites work. I did not change anything on my system. Mysterious...