This is probably caused by one of two factors:
To resolve problem one, change the permissions on the directories 'cache' and 'templates_c' in resources/smarty/ to '777'.
To resolve problem two, try using the default design theme 'Illuminux' that came with your software. If you've edited any of the template files that came with the script, make sure that your Smarty tags are correctly formatted with no mismatched curly braces.
To resolve problem three, place a {literal} and {/literal} Smarty tag before and after your JavaScript code to ensure that the Smarty template engine ignores the curly brackets in your JavaScript or CSS code.