Protools 11 & Mbox Pro have playback problem with Mbox Factory & Digirack 3 project
 

Hi all,
I am Avid newer. I am Hien Nguyen from Viet Nam. :D
I've just bought two Protool 11 & Mbox Pro products. When we use Protool and a Mbox Pro (1) to open and playback a project which record from Mbox Factory or Digirack 3, I hear some noise from Speaker. But when I export to file, It's still ok.
I tried with another Mbox Pro (2), It playback these projects OK or when I made a new project from old Mbox Pro (1), It's ok. I don't know where problem is and how to fix this. PLS help me, thank you. :(