I am using the "lock when sleeping" preference of the login keychain. When I use my computer after wake up, as expected i have to enter my password when an application (such as the webbrowser or instant messenger) try to access a keychain entry. However, sometimes the login keychain is unlocked after entering the password, sometimes it remains locked and the application gets single-time access. What rule does that follow? System is up to date 10.6.
There is a setting that can lock the Keychain after a period of inactivity. So if you have unlocked it after sleep and then find after a few minutes that it is locked, it probably means that this option is turned on.
It's also possible that on some items you haven't checked 'always remember' and so it is popping up the request for credentials via keychain.
You can also repair your keychain using this guide.