htaccess and pretty urls

Hello, I need some help with using friendly urls and an smf mod called pretty urls. Basically my site uses friendly urls but the forum is still using the old /index.php?38729783=2121 idea for the url and I installed the pretty url mod for my forum. It does the same thing as using friendly urls, it turns the url string in to a readable link but it’s not working with modx friendly urls.

Modx is installed in the root and the forum is in /community. If i go to /community.index.php?38729783=2121 it will show the forum thread and if I enable pretty urls which would make this /community/test-post, modx takes me to the error page as modx must assume /community/test-post is a page and infact is the forum post. I assume it would be able to work if I edit the htaccess file but I’m not sure what to do.

Could anyone give me an idea of what I should do?

thanks!