Thanks but disabling the plugin is hardly a solution!
Didn't say it was THE solution. It's step one of the solution.
First you disable the plugin. Did that work? Good! Now you know what's breaking! Next step is to tag the posts with the plugin.
Is it this one? http://wordpress.org/extend/plugins/wp-featured-content-slider/ If so, you add the tag
wp-featured-content-slider to your post. You also email the author. Remember, there are a LOT of similarly named plugins, so you have to be specific sometimes. It always helps to actually LINK to the plugin :) Disambiguate.
Check to see when the plugin was last updated. If it was pre 3.0, you may need to find a new plugin. If you MUST use this one, and the author doesn't help, check to see if
preg_match() is in the plugin files and maybe you can sort out why it's broken.
It's debugging 101, though, to turn it off and verify your guess is correct :)