Today I could no longer sign in to Windows Live Messenger from my work account, which is behind a firewall; instead I received Error 810003a8.  I did a quick Google search for the error code, which turned up nothing but an old thread on a New Zealand blog.  Because that thread is closed to comments, I decided to post my answer here and see if Google picks it up.  Maybe I can help some other poor soul in my situation!

To cut to the chase, the problem appears to be that the IP address of messenger.hotmail.com has changed, invalidating an earlier workaround I had implemented to allow Messenger to work through my corporate firewall.  If you find yourself in a similar situation, here’s how to resolve the issue.

The Solution

If Windows Live Messenger is running, close it.

Open the following file in Notepad or your favorite text editor:

C:\WINDOWS\system32\drivers\etc\hosts

Add the following lines at the bottom of the file:

64.4.9.254      messenger.hotmail.com
64.4.9.254      messenger.hotmail.msnmessenger.msn.com.akadns.netd

If you find any similar lines higher up in the file, delete them or disable them by inserting the string “# COMMENTED OUT” at the beginning of each line, like this:

# COMMENTED OUT 65.54.239.80    messenger.hotmail.com
# COMMENTED OUT 65.54.239.80    dp.msnmessenger.skadns.net

Save the file and close the editor.

Run messenger again.  It should work this time!