ok skype is p2p and therefor you need to go on the 9GB package or you use tunnels or socks proxies.
msn and irc, is different for everyone at the moment and I am investigating the reasons out of my own personal interest so I don't want to divulge all I know here but try this.
disconnect and reconnect to iburst, AS YOU CONNECT log on MSN or IRC (or you could try both at the same time), it must be as you connect, that connection should maintain as usual, and you wont get dropped. I know it sounds questionable, but try it.
if after you connect, say an hour after if you log off msn then log back on that connection will probably get dropped