Windows Live 7.0 Not Sending Messages? -

Hi, I m using Windows Live Messenger 7.0 to chat with Friends etc but lately its been refusing to send most of my messages (Returning the Error: This message could not be delivered to all recipients) And i know they are not receiving these messages either way. I m pretty sure its not something simple. We are both set to Online, They are just plain text messages, theres no settings ive changed lately. I ve considered upgrading it to the new version but i really hate all these Live programs so for the moment im just gonna go back to MSN Messenger 7.5 but is there a reason it is doing this. All the people i talk to on the other end are using MSN Messenger 7.5 And its only really been doing this since last night. My sister is also using MSN 7.5 on her laptop at the same time could this be causing any of the trouble? Well Thanks!

That problem is very popular, it follows an article of the micro$oft... http://support.microsoft.com/kb/839507/e...