The GMT setting in global options can match up the time but I dont think that would help thats just to correct post times. Your browser cookies are read by the browser.
what is strange on your site is the login works fine with the
vb enhanced interface turned off. You see this as well right?
So to me it comes down to something different about your
vb as far as I can tell. I cant replicate it on any of my sites or here thus far.