Thread:Project:Support desk/Can't Add More Than 4 External Links If They Have Labels

I'm building an internal wiki on my company's intranet. Here's our setup:
 * MediaWiki - v1.17.0
 * PHP - v5.2.17 (cgi-fcgi)
 * MySQL - v5.1.56

I can create a new page with up to three labelled external links, and everything works just fine. For example, this will work: Google Yahoo! Bing

However, as soon as I add a fourth link, I get a "403 Forbidden" error whenever I try to save the page. So, for example, this will not work: Google Yahoo! Bing MSN

If the fourth link is enclosed in square brackets without a label (i.e. ), I also get the 403 error. However, if I simply put in the fourth link as a URL without any brackets (http://msn.com) then I can save the page.

The full text of the 403 error is: Forbidden You don't have permission to access /wiki/index.php on this server. Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

What would cause this behavior? Is there a setting that limits the number of labeled, external links I can put on a single page?

Thanks in advance! I appreciate any advice or insight.