Facebook chat and messaging problem: Please help!?

This has been happening for a few hours now. I can see people online with the green dot next to them. However, when I try to send them a message in a chat window, I keep getting the message , 'An unexpected error has occured, please try again.' I've tried and tried a number of times but I still keep getting that message. Also, I can't even use the inbox feature and message people, it says 'Message failed to send'. I've sent emails to Facebook describing my problem, but it's unlikely that they will reply. This has happened in the past as well but when it has, it's happened to everyone in my area. Now, it's happening only to me. Is there any way to fix this?

Thank you