Dreamygirl,
I think I have the solution.
In the friendly Url Classes plugin, on line 26, the author uses an anonymous function (closure).
Code:
$stopwords = trim(implode('|', array_map(
function($x) { return preg_quote($x, "/"); },
preg_split('/(,\s*|\s+)/', $vbulletin->options['friendlyurl_stopwords'])
)));
Anonymous functions is a feature that was added in PHP 5.3, which means, servers running PHP 5.2.x would run into syntax issues - the exact issues that you and I are having.
I would advise you to test the plugin on a test server running PHP 5.3 to see if it solves your problem. If so, you may want to look into upgrading the current server from PHP 5.2.x to PHP 5.3 provided that it doesn't break anything else. If it does, then you will need to modify the code in the plugin to be 5.2 compatible.
This plugin works fine on our test server, which is running PHP 5.3.3. I'm almost certain this is the case, but I encourage that you test it for yourself before taking my word for it. I hope this helps.
-S