Apple just made a update for the Keychain in Leopard!
After the update restart is neededThe Login & Keychain Update 1.0 for Mac OS X 10.5 Leopard is recommended for all Leopard installations. It addresses issues you may encounter when:
Logging in with an account originally created in Mac OS X 10.1 or earlier that has a password of 8 or more characters.
Connecting to some 802.11b/g wireless networks.
Changing the password of a FileVault-protected account.