I have not been able to sign in to Windows Live Messenger for 2 days (it is critical for my job to be able to communicate with others overseas). I keep getting the following error message: "Signing in to Windows Live Messenger failed because the service is temporarily unavailable. Please try again later." The error code is 8000401a, which I can't find any references to anywhere. Can someone please help me fix this?

Have you tried reinstalling it?

Tried that, but I'm still getting the same messages. Interestingly, Windows Messenger works, but Windows Live Messenger doesn't.

If you are using AVG antivirus, do following:

* Open AVG interface
* Double-Click on the Web Shield
* Select the Instant Messaging tab
* Uncheck MSN Protection

Also if you uninstall and go back to msn 8.5 this problem should not happen
Download details: Windows Live Messenger (Version 2008)

My anti-virus is Trend Micro. I've had both it and Windows Live Messenger for quite a while, so I'm not sure what my anti-virus would have to do with my problem. I tried the download link you gave me, and I got the following message: There was a problem with this installation. Windows Live Suite was not installed. System Error Details: Code: 0x8000ffff Description: Catastrophic Failure

Have a look at this link.

Hopefully some solution works from there for you. I am guessing its most likely registry error discussed on second page.

First, make sure you have exited MSN messenger and unsinstalled any MSN Messenger related entry from Control Panel (START — > CONTROL PANEL — > ADD OR REMOVE PROGRAMS).

Then, START — > RUN the following command:
RunDll32 advpack.dll,LaunchINFSection %windir%\inf\msmsgs.inf,BLC.Remove

Try this link to download 8.5
http://messenger.jonathankay.com/redir/wlm85.asp

Not sure what I did, because it never looked like messenger installed when I ran wlm85, but it works now. Thank you seahwk83!