Save Menu button causes Internal Server Error

I’m running WP 3.2.1 (updated from an install that is about 4 months old.) The WP site is hosted from godaddy’s linux hosting service. I have the following plug-ins installed:
WordPress Database Backup
Quick Chat
Fast Secure Contact Form
Exec-PHP

I’m using the Zombie Apocalypse theme.

Life seemed to be good until the weekend that a bunch of pages were created. The website is not really used as a blog. It’s mostly a collection of about 30 pages under a single menu. When I go to Appearance>Menus in the admin panel, add a page to the menu, and click “Save Menu” nothing seems to happen for a few minutes. After a long wait either I get an Internal Server Error that says this:

“
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.\
Apache/1.3.33 Server at http://www.necroratus.com Port 80
“

Or I might get a blank white screen.

This occurs when I use IE or Firefox. It occurs when all plugins are disabled. At this point, this happens about 99% of the time.

My database has been optimized and the rest of the page seems to be functioning correctly (except for the update button on the “edit page” page which is behaving similarly.)

I’m not sure how to troubleshoot this any further. Does anyone have any recommendations or useful information?

Thanks for reading.