HTTP Error 500

Hi there, I have just installed Mail Alerts and went to configure the settings but I get this error when I click on any of the Admin buttons.
<blockquote>Server error
The website encountered an error while retrieving http://www.xxxx.uk/administrator/index.php?option=com_jmailalerts&view=sync#. It may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later.
HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.</blockquote>

Suggestions appreciated