Why my friend can't sign in his msn on his msn messenger ?

uninstall and install msn again if its because password forget then make new msn address

I had the same problem use a program called trillian. you can use AOL. Yahoo and MSN on one program. Its pretty cool and you dont need hella programs to run IM. http://www.trillian-messenger.net/ that is the site for it. oh, I think i should get a best answer point for this lol. no for real, i should

Mine done the same so i uninstalled it and then reinstalled it and now it works fine. I suggest you try that.

That sometimes happens to me. It says error can't log you on. Trouble shooting doesn't help. I usually wait for 2 days or so. But that is awkward. Maybe you should go and ask for MSN help with the Staff.

Try resetting the timezone of the laptop. Sometimes if the timezone has been changed it can do funny things to your computer. After mine got fiddled with one time I found I couldn't sign into msn or full tilt poker or access some specific websites.

tell to try and reinstall messenger then give it a go or might be a dodgy connection

The time and date on the laptop must be correct for MSN to work.