Some more info in the hope of helping make this simple to crack.
You talk of changes to the htaccess file, we don't run that, I checked with you the other day and you said we didn't need to.
I think this is probably actually some very simple bit of code. You won't see it on your system or on any new install as it only shows when you have more than 12 members on a single letter on the members index. Your site doesn't have that and like yours my site works just fine with under 12 users on a single letter.
Anyway... on to hopefully a solution...
If I choose H from the member list to only show members starting with H the link I go to is this one:
Works fine every time and shows first 12 members starting with H.
The No 2 page link under those members is linking to this:
That is wrong and the problem. It takes you back to the full members list and not just those starting with H.
I tried making up a likely looking link and entered this URL....
Worked perfectly and is all that is needed to fix this whole problem I think.. just a minor change to the link being produced.
I've tried to find where these links are created and it seems likely to be here (though this is a total guess and I could be totally wrong
pp-inc.php(2063): $posternav .= "<a href=\"" . construct_newppurl( "showmembers.php", array('cat' => $cat, 'page' => 1) ) ."\">1</a> ... ";
pp-inc.php(2089): $posternav .= "<a href=\"" . construct_newppurl( "showmembers.php", array('cat' => $cat, 'page' => $p) ) ."\">$thispage</a>";
Is there a simple change that can be made to make it work as normal again?
Thanks for any help you can give, it would be great to get this working again.