Because the Keychain manages so many different pieces of information, it may eventually develop minor corruption, causing problems—for instance, the e-mail client may repeatedly ask for your account password, or the Keychain may fail to save your .Mac password.
When this happens, you need Apple’s Keychain First Aid. In Mac OS X 10.3 and later, you’ll find it in the Keychain Access Window menu; if you have an earlier version of OS X, you must download it as a separate utility from Apple’s Web site ( find.macworld.com/0104 ).
To repair your Keychain, enter your user name and password, select Verify, and click on Start. If the utility finds any problems, you’ll see a description of each and you’ll get a prompt to repair them. Select Repair, and then click on Start. (An administrative user can also verify and repair other users’ Keychains, though without the ability to see the details.)