I had this issue, i think i have sorted it so i will share with you guys.
Make sure you have your permissions allowed in your usergroup prmissions first
in your ACP => Photoplog => Modify Settings
The photoplog link should read:
http://www.yourdomain.co.uk/forums/photoplog
Then go to
ACP => Vb options => cookies & HTTP Header Options
Path to save cookies to should be: / or if you installed photoplog inside your forums directory /forums (or whatever your is) but / is good for all.
If you don't have this, then fill in the custom settings box.
On same page go to
cookie domain and use custom setting to enter: .yourdomain.com (two dots but no www and no http)
Save off and it should have worked.
