Need Daw Assistance, problems with playback in PT LE 6.9.2 Options

[guinness drinker]

First time forum user so bear with me. I have a G4 powerbook running Mac 10.4. I just upgraded to PT LE 6.9.2 from 6.2.2 and purchased powered studio monitors. I have never used my Mbox for playback of iTunes etc... but am trying it now. I connected the Mbox using 1/4" to XLR cables from the Mbox (line out on the back) to the monitors. I configured my sound prefs to Mbox DW for both input and output. All i get is garbled nonsense during playback. I also imported a track to a PT session and played back. Same deal. I am probably missing something in the setup but need some guidance. The digidesign core audio manager sees the Mbox connected. Is there any other setup necessary? Help!!! I was monitoring playback in the past using the headphone jack on the front. Thanks in advance.