It has nothing to do with photopost since we dont have a login.php file in our distribution in any manner you can check that out pretty easy.
vb loves to try and blame up for their issues although this has nothning to do with photopost or vbulletin if you want the facts about your issue which by the way is already fixed as I stated above.
You are using some custom vbulletin style and your using a relative link in your footer which is some vb2 throw back since vb3 has all the login stuff in the navbar usually at least in a non modified
vb 
and as previously explained by email and even in this thread you can not use relative links over another application. You must use full urls for program files to be found when your dealing with other directories. Remember we have had this discussion before via support threads. Remember your blog.php link went nowhere before I explained how you where using again relative links in your
vb navbar template and I fixed that issue for you.