Photoposts forums suck, it takes days to get a response if you get one at all.
Actually - I submitted a post there about messed up cookies and I got an answer within 30 minutes from the Photopost Custom Developer and Support Engineer. They have been very efficient and timely with me at least.
As for the problem - It looks like you are having problems with installing it. I would check all your database settings and your CHMOD's for the directories and see if that doesn't fix it. I integrated 4.8.1 with a vB 3.0.3 just the other day and it worked fine for me. If you want me to take a look send me a PM or AIM and I can try and help you out.