Windows Live Messenger

Hello,
I am experiencing trouble with Windows Live Messenger on my computer, Whenever I open it and try and login it always stops working. If you know how I can fix this please reply. I am also having trouble with downloading Yahoo Messenger and other stuff.When I try and download it says it cannot connect to the internet and I check the connection and it is working perfectly, I don't know how to fix this. If anyone can tell me how to fix this please reply :D pce!