Try reuploading the latest files and reinstalling (without uninstalling) the product. If that doesn't work, edit the "Finalize BBCode" plugin that uses the "newpost_preview" hook and replace this:
with this:
PHP Code:
header('Content-type: text/plain');
die('quotes = ' . print_r($quotebbcodeids, true) . "\n random = " . print_r($randomquotes, true));
}
Then try previewing a post with a few [quotes] and [randomquote] bbcodes in it and tell me what the output is. This will break the post preview, so undo the edit after you're done.