Hi,
Welcome to the Discussions
Can I clear up a few terms first to make sure we are on the same page ?
Logging In or Out normally refers to the Screen Name you are using to gain access to the Aim or any Jabber Server you have an ID with.
Logging Out can be down two ways.
Going to the iChat Menu > Preferences > Accounts and Deselecting the "Use this Account" check box.
Or from the iChat Menu > Accounts and selecting any Ticked account name will toggle it off.
Logging in can be either the reverse of the two above or when you start Up iChat.
Now by default iChat tends to Save the Password for any Screen Name/Account you have so that when iChat Starts Up
AND the setting in the General Section of the Preferences is set to Make you Available at iChat Launch then you will get Logged in.
I suspect you mean the latter.
You can remove the password from it's stored place AND iChat so that in the future you have to enter the password each time.
Use the second part (Next Step) in this Users Tip to Access the Keychain and remove the password for your Screen Name(s)
http://discussions.apple.com/thread.jspa?messageID=607493
9:44 PM Tuesday; February 9, 2010
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"