Hello,
Each time I try to change a title or a description I can't save it and I get a error message instead (see bellow). I have been running this gallery for a long time and it happened out of the blue. Any idea? Thank you.

Zenphoto version 1.3.1.2 [5831] (Official Build)
Current gallery theme: zpGalleriffic
PHP version: 5.2.17
Graphics support: PHP Imagick library 3.0.1
ImageMagick 6.7.6-8 2012-05-02 Q16 http://www.imagemagick.org
PHP memory limit: 96M (Note: Your server might allocate less!)
MySQL version: 5.5.23

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, webmaster@compostela-images.compostela.us 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.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Apache Server at www.compostela-images.com Port 80

First note that 1.3.1.2 is not the current release. Whatever we will tell you will be based on 1.4.4.5. So you should upgrade.

Internat server errors most likely are related to a wrong htaccess file. Either you have modrewrite enabled without having server support or it is the wrong one. But on the backend modrewrite and therefore htaccess is not used at all.

So you have to look into the server error log for some proper errors. Or contact your host.