permalinks bug?

Hi,

I have tried to find the solution all over the internet, without success.

I have recently upgraded my WordPress installation to 2.3.3.

Almost everything is working, except the tags permalink.

http://www.site.com/tag/art – Gives a 404 error.
http://www.site.com/?tag=art – Works perfectly.

http://www.site.com/category/paint – Works perfectly.
http://www.site.com/?category=paint – Works perfectly.

If I set my WordPress to use the ‘default’ permalink structure, everything works properly.

If I define a custom permalink structure (/%postname%.htm), the above error rears it ugly head.

My .htaccess is defined as per the suggestion on the permalinks page:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

I do not know what I am missing, to get the /tag/art permalinks to work, but your suggestions are welcomed.

I have considered the possibility that I may be running into a bug?

—
Regards,
Carl