Check your firewall settings, most likely you just need to make an allowance to your messenger services.
I have a dell inspiron 1501 with windows vista. I am having problems logging into any messengers. I can log into yahoo for mail and homepage, but when I try to log into messenger, I get a "try again later" message. I thought it might just be an issue with yahoo, so I also tried windows live messenger, same problem there. I have tried emailing yahoo help, with no luck, I have tried contacting dell for assistance, still no luck. I have tried all the different settings, I have tried looking into the ports, but I am a newbie to the computer thing, so I am having issues. If anyone is out there that can help me through this I would appreciate it.