I'm not an expert by any means but you can try:
[code]
loctation /forums {
rewrite ^/forums$ /index.php last;
rewrite ^/forums/$ /index.php last;
rewrite "/forums/([-_a-zA-Z0-9]{3,30})$" /forums/$1/ last;
rewrite "/forums/([-_a-zA-Z0-9]{3,30})/(.*)$" /phpBB3/$2?access_name=$1 last;
}
[/code]
It's possible someone on the phpBB boards has solved this. If these don't work you can try there.
--
Jim Ohlstein