To sort out your yahoo messenger problems please read carefully this detailed solution

Hallow Friend,
If you have tried restarting your computer,signing in with your Yahoo e-mail prefix (without the @yahoo.com)and your e-mail password without success, and you are sure your caps aren'tlocked and your information is correct, your Yahoo! Messenger connection information maybe incorrect. Follow these steps to configure your connection:

Solution 1.) Click theMessenger menu in Yahoo! Messenger and select "ConnectionPreferences."

Enable the "Firewall with no proxies" option.

Select the correct Internetconnection type and country from the pull-down menus.

Click the OK button at thebottom of thewindow.

Yahoo! Messenger will ask you if you want to sign in again with your new proxysettings. Click the OK button.

Enter your Yahoo!ID and password and click the "Sign In" button.

The above configuration works in most situations. (However, if you connect inthis way, you won't be able to use the Voice feature.) If this configurationdoesn't work, follow these steps:

Click the Messenger menu in Yahoo! Messenger and select "ConnectionPreferences."

Enable the "No network detection" option and then click the OK buttonat the bottom of the window.

Yahoo! Messenger will ask you if you want to sign in again with your new proxysettings. Click the OK button.

Enter your Yahoo! ID and password and click the "Sign In" button.

If neither of the above options work (sorry), you're probably behind a firewallor proxy serverthat requires you to enter its address. Follow these steps:

Click the Messenger menu in Yahoo! Messenger and select "ConnectionPreferences."

Enable the "Use proxies" option.

Enter your firewall or proxy server's address and port number. Contact your network administrator(if you're at work), or your Internet service provider (if you're athome) to determine the correct firewall and proxy settings.

Click the OK button at the bottom of the window.

Yahoo! Messenger will ask you if you want to sign in with your new proxysettings. Click the OK button.

Enter your Yahoo! ID and password and click the "Sign In" button.

If you try all of the steps above and Yahoo! Messenger still can't connect,contact your network administrator, Internet Service Provider (ISP), or theperson who initially set up your computer to ensure that your firewall and/orproxy settings are correct.
http://help.yahoo.com/l/us/yahoo/messeng...

Solution 2.) You may have accidently saved your ID or password with errors init. To resolve this issue, clear your cache.

For InternetExplorer:
Click on: Tools
Click on: Internet options
Click on: Delete Cookies
Click on: Delete Temporaryfiles

For Firefox:
Click on: Tools
Click on: Clear private data
Check: All the boxes
Click on: Clear private data now

Now try to log onto Yahoo Messenger.

Solution 3.) If Step 1 and Step 2 don't solve your sign in issue, tryun-installing then re-installing Yahoo Messenger:

Close Yahoo Messenger
Click on: Start
Click on: ControlPanel
Click on: Add/remove programs
Locate and remove Yahoo Messenger

Download Yahoo Messenger:

Yahoo Messenger for Windows:
http://messenger.yahoo.com

Yahoo Messenger for Vista:
http://messenger.yahoo.com/windowsvista....

If you are still unable to sign in, on Internet Explorer:

RESTART YOUR COMPUTER

If that doesn't help, here is a link to Yahoo Help:

IMPORTANT: If all of the above does NOT solve your problem, here is a link to Yahoo! MessengerHelp Form:
http://help.yahoo.com/l/us/yahoo/messeng...

For future reference, please note there is a link to Yahoo Messenger Help atthe very top of your Yahoo Messenger!