This issue is caused by using the incorrect version of PHP. You must have at least PHP5 in order to use JFBConnect, as described on the product page.
We have posted in the forums on different methods to upgrade PHP depending on your hosting company, and we'd recommend doing it anyways as most new software is starting to require it. Joomla 1.6, for example, requires a minimum of PHP 5.2 to run.
This post may help you get started:
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