Used Permalinks, Now 404 File is Messed Up

Hey guys, this is an odd situation I think I’ve found myself in. So recently I changed my WP blog to custom permalinks, and had to edit the .htaccess file to get it to work. I had to add the small batch of code provided when I updated the permalinks to the htaccess file, and everything was okey dorey. Now, my blog is in its own folder (/blog), but now instead of giving me the custom 404 error file that I created for errors, my domain acts like I’m trying to access some posts in the blog, and takes me to the blog’s “Search Not Found” page. It doesn’t matter where my error came from (the root, another sub-site in another folder, etc), it keeps coming back to the /blog “No posts found” page. I’m pretty sure it’s because I had to add the code to my .htaccess file.

How can I fix this, so I errors will go back to my custom 404, while still keeping the permalink structure for my blog?

This is what I added to my htacess:

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

Anyone know how to fix this?