I have the same problem. I am on a Movistar network. I sometimes get the black clock but recently i am having to wait between 3-5 seconds before i can unlock my cell. I have it password protected and it takes 3-5 seconds before the unlock menu comes up.

I am really frustrated with the OS which I think is causing the problem. I encounter this latency when i switch tap on emails or between groups in bbm. Is there a fix for the OS coming soon?