Archive 404s

I have an error with my WP1.5 arcives – the archive links – http://www.domain.com/blog/2005/04/ – generate a 404 error – with a log entry – [Directory index forbidden by rule]

.. but all other permanlinks work correctly..

eg: – http://www.domain.com/blog/category/general-news/
and
– http://www.domain/blog/2005/03/24/postname.html

I did have this problem on a previous install and it was “cured” by editing the permalinks format and forcing the .htaccess to be re-written… but I cant get it to work this time.:(

I have..
– removed permalinks
– added them back
– changed the structure of the permalink tags
– deleted the htacces and forced a re-write
– read multiple messages here in the forum

but I cant seem to find a cure;(

Any help appreciated – TIA

DD