Just an update on the above. Members may want to realise that the search table has now been renamed to searchids as of v5.61.
Also, I think an important first step has been left out of the above instructions.
You need to go into your photopost admin area and change "Forum database table prefix" to whatever you are changing it to. If you rename your tables prior, then the whole system will break and you wont be able to get into admin or even view your gallery.
Can a member from Photopost please confirm this?