OK - just when I thought this was fixed, it's not.
I know you said there's a lot of info around and I accept that, but given the circumstances of when it happens I'm puzzled. I'll go and search for that info again, but in the meantime this is what's happening:
If I go to the index page it shows the latest photos (the last 20). If I click on the latest one, no problem - it displays and if it has a larger version that works too.
But if I choose the link on the index page to Recent Photos: 7 days
for example and click on that very same photo, it gives the error shown in the first post on this thread above.
The only difference between the photo on the first page and the one on the 7 days page is the info being passed.
The first one works, the second one gives the error.
If I paste that second one on a new browser, it gives fatal error. If I remove the cat=last7 it works fine.
(my forum is not publicised - if supports needs to location of my forums with a login let me know and I'll pm the info).