A corrupted cache can stop users from signing into Windows Live Messenger 9.0 (2009) with their Live ID accounts. According to Microsoft, some users seem to be getting an error 8100030d when they try signing into Windows Live Messenger, in some cases after they have upgraded to the latest version. This error can be caused if the cache files get corrupted and the solution is to simply delete the cache.
“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 and C:\Documents and Settings\ Your Windows logon name \Local Settings\Application Data\Microsoft\Windows Live Contacts\ Your Messenger email address,” Microsoft explained.