On install you must enter two things to be able to login correctly. On the first step of install is the vb
license number. The next is on the next to last step of install is enter the vbulletin cookie prefix which by default is bb. You can find your vbulletin cookie prefix and license number in your vb
config.php file which is located in the vbulletin install includes directory. Since both the cookie prefix and license number are encrypted along with the password to form the password cookie this is why you do not authenticate. I would suggest you rerun install.php and input the information.
You must change your forum email to match that of the license on file for photopost. Only verified customers are allowed certain access on our site. This thread should explain this in detail. http://www.photopost.com/forum/before-you-buy/announcements.html