Pretty Permalinks Cause my Non-WordPress Pages to Give 404

I use WordPress 2.3.1 as part of a bigger site and have it installed in its own subfolder.

At the root, I have an .htaccess which does url rewrites for the non-wordpress part of the site.

The rewrites work great for non-wp until I enable pretty permalinks. They continue to work but the custom rewritten urls give 404 responses.

I use the same index.php to power the whole site. Could wordpress be issuing the 404 headers?

Now I have disabled the permalinks until I find a solution.

My non-wp rules are like this:

# Add Trailing Slash
RewriteRule ^items/([-a-z0-9]+)$ /items/$1/ [NC,R=301,L]

# Main Rewrite Rule
RewriteRule ^items/([-a-z0-9]+)/?$ /index.php?page=items&item=$1 [NC,QSA,L]

As you can see, the custom rules are fairly standard stuff, and are kept in their own htaccess at the root. I don’t know why wordpress, which is in its own subfolder, should interfere with them.

Appreciate your ideas.