Passing parameters in the query string causes a 404

I'm having a really strange problem. The following page, which is going to be a search results page, loads fine on its own:

http://www.kansaspancake.com/search

However, if I add anything to the querystring, I get redirected to my 404 page:

http://www.kansaspancake.com/search?q=test

Anyone know what could be causing this? Here's everything I can think of that's unique about this site:

• This is a multi-context site. There will eventually be 50 domains (one for each U.S. state) all pointing at the same Revo install, with a custom switch statement in the index file that directs to the appropriate context.
• Friendly URLs are turned on.
• There is no suffix for the html content type.
• I have Redirector installed but am not using it.
• I wrote a custom plugin that fires on 404 events, checks the users table for a match, and either sends them to a view user page or to the 404 page. The page it's used on works fine, even with a query string. However, this problem doesn't go away even if I disable the plugin and clear the cache.

I've seen this on windows servers, if your on windows what's in your httpd.ini? Or whats in your .htaccess?

I'm not sure, but "q" can not be used as a query parameter.

If you are using MODX friendly urls, q is the query string parameter which identifies the page to load.

Oh man...I learned something today! You're absolutely correct -- using q was the entire problem. So obvious, yet I had no idea. Thanks, everyone!