I opened the ports and have been using CrafBukkit for about a week now. But when starting it up, it claims that it can't bind to the port and that it might already have a server running on it. This hasn't happened during the week I've been using it. The official server software (One from Minecraft.net) works perfectly fine. It wasn't running when CraftBukkit claimed to not work. Restarting my computer does nothing. Last time I had this problem, I restarted my computer to close all the programs and it worked. My friend suggested restarting the router, just did that, nothing happened. I'm on a Mac running Mac OS 10.6.7 and using CraftBukkit build #818. I was thinking of updating to build #835, but it doesn't say it's recommended.