How to Move Servers and/or Change Directories
I think you really need to follow that thread and make sure everything is done correctly. Make sure your forum is all new files not hacked no plugins deal with the simple for now. Make sure its connecting to the new database on the new server etc in there config file.
Then check your photopost config. To my knowledge everything if setup right should provide an accurate login. You can always as suggested ask vbulletin. Your issues are coming from vbulletin login.
Login - WFC Foto Beeld, de interactieve foto site van Nederland
I login to the gallery fine here and the proper cookies are made. Are you using some type of other stuff besides a normal
vb? Obviously tracking down other changes you have made are going to help you.