It sounds like you might have a [zombie process] (http://en.wikipedia.org/wiki/Zombie_processzombie process). This is harmless: the only resource a zombie process consumes is an entry in the process table. It will go away when the parent process dies or reacts to the death of its child.
You can see if the process is a zombie by using top or the following command:
ps aux | awk '$8=="Z" {print $2}'