When you launch Windows Messenger and try to sign in to the service error code 81000378 is displayed and prevents you from signing in successfully.
Do not despair because You cannot use Messenger at this time ...
The error code can be caused by the server that stores your Contact List being busy or being down altogether or a problem with your connection with the Contact List server. There are a few troubleshooting measures you can take to try and correct the error problem.
If you cannot access your Contact List in Windows Messenger it may be because you cannot connect to the server to download the list. This method of troubleshooting involves adjusting the settings in Internet Explorer. You can do this by launching Internet Explorer and then clicking on Tools
on the toolbar at the top of the browser window. Click on Internet Options
on the pull down menu under Tools and then choose the Advanced
option. Scroll down to Security Settings
and remove the check mark next to Check for server certificate revocation
and then check to ensure the Use SSL 2.0 check box is selected and the Use SSL 3.0 check box is selected. Close the Internet Options window by clicking on OK.Try to sign in to Windows Messenger again.
If you are trying to sign in to Windows Messenger in Windows Vista it is necessary to run a series of commands to try and correct the error. Click on Start on the main toolbar and when the Search box appears enter regsvr32 softpub.dll and then press the Enterkey. You will see a message that says DllRegisterServer succeeded after you enter the command. You will wait for this message each time you enter the following commands: regsvr32 wintrust.dll regsvr32 initpki.dll regsvr32 Rsaenh.dll
regsvr32 Mssip32.dll regsvr32 Cryptdlg.dll regsvr32 Dssenh.dll regsvr32 Gpkcsp.dll
regsvr32 Slbcsp.dll regsvr32 Sccbase.dll These steps will re-register the necessary .dll files for Windows Messenger. When you are finished, close the window and try to sign in to Windows Messenger.
TipFor further information please read: How to fix Windows error #0x10010000