I finally got photopost, classifieds and
vbseo to work.
vbseo does not rewrite the photopost and classifieds urls. They only rewrite the main forum.
When I first installed
vbseo when photopost and classifieds was already installed, all of my links pointed to a page that didn't exist. Turning
vbseo off would make everything work again.
It turned out that my hosting company needed to have mod_rewrite installed on my server. Once they did that, everything now works perfectly.
vbseo rewrites my main forum and photopost and classifieds work off of their own rewrite system.