Windows Live forum: Windows Live Messenger error 800030d

It's not a firewall that's blocking MSN. I have cheacked. Do you have any other ideas?

It's only my e-mail address that doesn't work. The other e-mail addresses work for some reason.

I happened to fix it. Just look under on how to fix it.
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2.b.i. For Windows XP
Right click on the Start button and then click Explore to open Windows Explorer. On the Tools menu, click Folder Options. Click the View tab. In the Advanced settings list, select Show hidden files and folders under Hidden Files and Folders. Click to clear the Hide extensions for known file types check box . Click OK to close the Folder Options window.
Delete the Contacts Cache folder. To do so, right-click Start, and then click Explore to open the Windows Explorer window. In the Windows Explorer window, locate the folders below and delete all the files and folders inside them
C:\Documents and Settings\ Your Windows logon name \Contacts\ Your Messenger e-mail address
C:\Documents and Settings\ Your Windows logon name \Local Settings\Application Data\Microsoft\Windows Live Contacts\ Your Messenger email address

Note: Windows Logon name is the logon name that you use to sign in to windows. Your Messenger email address is the address that you use to sign in to Messenger.

2.b.ii. For Windows Vista
Click Start and then click Explore to open Windows Explorer. On the Organize menu, click Folder and Search Options. Click the View tab. In the Advanced settings list, select Show hidden files and folders under Hidden Files and Folders. Clear the Hide extensions for known file types check box. Click OK to close the Folder Options window.
Delete the Contacts Cache folder. To do so, right-click Start, and then click Explore to open the Windows Explorer window. In the Windows Explorer window, locate the folders below and delete all the files and folders inside them.
C:\Users\ Your Windows logon name \Contacts\ Your Messenger e-mail address
C:\Users\ Your Windows logon name \AppData\Local\Microsoft\Windows Live Contacts\ Your Messenger e-mail address

Note: Windows Logon name is the logon name that you use to sign in to windows. Your Messenger email address is the address that you use to sign in to Messenger.
(Credit: http://messenger-support.spaces.live.com/blog/cns!8B3F39C76A8B853F!13937.entry)
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Now uninstall your current version of Windows Live Messenger (don't update or repair) and download the latest version off the site and install it. It should work now.

It should work now.