Audio records fine, only "hiss" on playhback????

[whinason]

My setup:
iMac 3.06, 2gb ram, nvidia 8800gs 512, Leopard 10.5.8
LaCie 4 big Quadra firewire drive
M-Audio ProFire 2626, vers. 2.2.4
PT M-Powered 8.0.1

Successfully recorded 20 seconds of audio using microphone, input 1. I can hear the audio while recording, see the waveforms, no problems so far. Stop the recording, waveforms are there, all is fine so far. Press play for playback, nothing but a constant hissssssssssssssssssss. No recorded audio is heard what so ever. All Hiss.

Troubleshooting steps taken:
-If I navigate to the session audio folder, the audio recorded fine. I can play the audio clips (in finder) with no problems. This tells me the hiss is not recording.
-I have trashed all preferences according to digi instructions (twice)
-I have all the latest versions, drivers, etc. (described above)
-I have tried several firewire chain combinations: FW400 from iMac to 2626 unit, then chain the drive FW400 from 2626 unit. AND: FW400 from iMac to 2626 unit and FW800 from iMac to drive. Hiss occurs either way.
-Turned off airport, bluetooth, ethernet, firewire networking, energy saver
-Deleted databases and volumes
-disabled spotlight indexing on audio drive
-rebooted, rebooted, rebooted

I am at a loss.

Can anyone help? Did I miss a step?

I promise I searched the DUC before posting. If I missed a thread, I'm sorry. Send me a link to the thread if there is one.

Thanks in advance

Jason

[whinason]

An added note,

I just tried recording in Soundtrack Pro using the ProFire 2626, everything worked great. Records and plays back with no issues. This tells me it's a PT M-Powered issue, not an M-Audio ProWire 2626 hardware issue.

Any suggestions?

Thanks again,

Jason