HELP NEEDED: Signing in failed because the service is temporarily unavailable

I have been using Microsoft Messenger for about the last
four months. I haven't had any problems with the service. I
use it with a webcam and microphone to video and voice
conference call. I have Microsoft Messenger version
4.7.2009, which came with my Microsoft Windows XP Home
Edition. It's great!

About a couple of weeks ago, I started getting the
following message when I attempted to login to the
Messenger Service:

Signing in to .NET Messenger Service failed
because the service is temporarily unavailable.
Please try again later. Click the Help button
to check the current .NET Service status.
Retry Cancel Help

When I click help, the Service Status for .NET Messenger
Service is listed as "All systems are stable and running."

This problem has been persistant over the past couple of
weeks. Every time I login, this message appears. So I've
been unable to login at all, even though the overall
service status is reported as running.

I've tried uninstalling & reinstalling Messenger via the
Control Panel. I've tried reinstalling via the Messenger
download/upgrade website. I've tried disabling my Norton
Anti-virus. I've done registry scanning and cleanup using
System Mechanic 4. My PC is also pretty much up-to-date
with Windows XP updates, as well. Nothing has resolved my
problem and it doesn't seem to be going away by itself.

I am having no other problem with my computer besides this
new sign in problem. I use a 56K dialup connection for
internet access. There's been no change in my dialup access
numbers or problems with my internet connection.

Finally, two days ago I opened a support ticket at
http://messenger.msn.com/help/contactus.aspx, but I haven't
yet heard back. Any suggestions would be quite welcome!
Thanks so much. Cheers!