I just turned on FileVault after upgrading to OS X 10.9 on the mid '12 MBP I got this week and I believe it is causing keychain problems. Yesterday I called Apple support and the tech helped me reset the default keychain a couple of different ways after running First Aid for it. This solved the problem of several processes repeatedly asking for the keychain password in an endless loop. Today the Calendar agent and one or two other things (processes? applications? services?) are still asking for the keychain password albeit very intermittently. com.apple.iCloudHelper.xpc Keychain Access These are two I've noticed so far. I asked him if this was in anyway caused by enabling FieVault, but he said no its just a coincidence and that they were unrelated. My stubborn mind still thinks otherwise. Anyone had this issue? Once again, thanks for any help and/or advice! Also I just noticed that FileVault still had an hour or so to go with its encryption.