OSX is repeatedly asking for login keychain password
It sounds as an issue either with the Keychain App. Try repairing it. To do so just:


Locate the Keychain Access application, under /Applications/Utilities.
Choose Keychain Access > Keychain First Aid.
Enter your User name and Password.
Select Verify and click Start. 
If any problems were found, select Repair and click Start again.


It could be, too, that you've changed your account password without using the Accounts Preferences pane. If that is the case, for your default keychain to be unlocked automatically when logged in, you'll have to Synchronize your Keychain Access and login passwords. To do so just:


Open Keychain Access. 
From the Edit menu, choose Change Password for Keychain "login."
Type the former password of the account that you are currently logged in to, then click OK. 
If you entered the correct password, a new window appears; enter the original password again in the Current Password field. 
In the New Password field, type the password that matches your current account password.
Re-enter the newer password in the Verify field, then click OK.


This is needed because, as Apple explains it:


  If you change your account's password using your Mac OS X Install disc (or if your network-based account password is changed due to a network admin forcing a password change), your default keychain password (which uses the same initial password as your user account) does not change. Because of this, you will be prompted to enter a keychain password each time an application requires authentication that your keychain would normally provide.