hmmm? so that's probably why my original phpbb structure tables did work.
Phew, I doubt I would probably ever have thought about the indexes
Would REPAIR tables be able to solve this completely?
Added:
hmm, I might as well try it
Added again:
Nope: repair didn't add indexes
But I checked my version of phpbb_acl_roles (which is an original phpbb 3.0.11 table to which I transfered the data from the non-working copy) and that has the indexes. (although I can't be sure of whether the index dat was created during the transfer of data or later when I repaired all tables).
So my analysis is that Marc hit it spot on!! :thumbsup