403 Forbidden Error when Previewing/Posting

[Bunny Foo Foo]

I recently installed a new board that's version 1.0.5 onto My site and I've had a few users reporting a weird issue with it.  Some of them, when trying to preview their post, or post it are being redirected to a 403 Forbidden page telling them they don't have permssion to access the page on this server.  One user having this error found it was being brought on by a word she was typing in the post.  When she took out the word, the error went away and the post went through as normal.  She still cannot make a post using this word (which was "curl" by the way) because she receives the error every time she tries.  I thought maybe it was the word, but I can post it without a problem.  I have another user having the same problem and advised her to try going through the post and seeing if she could find a word bringing on the error but as of yet she hasn't had the chance to try.  She also had someone try to make her post for her, wondering if maybe it was just her computer/server, and he received the same message when trying to make the post.

All of the users have no problem making typical posts on the board.  I've checked to make sure all the permissions are set up properly, and also made sure that it wasn't something with the censored words.  This particular board is set up as a role-play forum, so having to go through and search posts for problem words is irritating and tedious when the users go through often great lengths with the time and effort put into their posts.  I have no idea what could be bringing on the error or what to do to fix it, as I'm only minorly technically inclined when it comes to coding.  Does anyone have any idea why some of My users are getting this error and what needs to be done to fix it?  Any help would be greatly appreciated because I'm completely stumped.

[xenovanis]

For example, if I were to post this:

Have you ever used cURL?  You can find information about it at http://curl.haxx.se/.  More specifically, libcurl is useful for accessing URLs in a program - it could be helpful if you're a programmer.

On a server with mod_security enabled, I'd get an error.  This error wouldn't be preventable by SMF, because it's created by the server and Apache, before SMF even gets a say in anything.

Having problems with mod_security?