[Darryl Ramm]

By all means switch to Garage Band and you should have a lots less chance of making mistakes getting started, and its a lot lighter on system requirements than Pro Tools. And its a pretty good/fun simple DAW especially if you are more doing composing/creating vs. tracking and audio mixing.

Unfortunately you do seem to have an underconfigured system and have provided little useful information about it or exactly what you are doing.

It looks like you did not worry about meeting the Pro Tools minimal system requirements before trying to get started. Often when that happens, it also means you are also likely have not followed install instruction, not optimized the system, may have out of date/incompatible plugins, etc. So we need to check all that stuff out.

Do you have a dedicated audio/session drive or not? Is that what the external 500GB drive is for? What is the specs of that and every other drive on this system? Make/model/rpm (all from the System Information Utility). This external drive is Firewire or USB 2 or what exactly? If it is Firewire how is it chained to the Digi 002. Describe every cable or adapter between the Mac to whatever is last in the chain? I cannot understand all the story about this external drive. Have you been recoding to it or not? Who or what told you it needed to be reformatted and why? Just becuase you brought a drive with a Windows NTFS filesystem on it or something else? And I especially care if its' a Firewire drive and you have not been using it but it has been in the Firewire bus chain, even if it is not powered up

3GB memory configuration in a Mac seems a little strange and underconfigured for lots of modern things. Memory is cheap and if you want to keep this Mac you probalby want to look at maxing out memory. Although that won't affect this immediate problem.

If you really want help here you will need to prove clear useful information about your system. Start by reading the "Help us Help You - READ THIS Before Posting!" link on this and every other DUC page.

We need at least answers to the following... take your time, quote this post and reply in line to each question.

Is anything else connected to the Firewire bus?

Has this Digi 002 worked reliably on other computers and/or Pro Tools installs?

What standard troubleshooting steps have you tried? (e.g. tried other Firewire 800 to 400 adapters, Firewire cables, tried reversing Firewire disk and interface chaining orders, tried removing all Firewire peripherals except the interface? trashed prefs and databases? uninstalled and reinstalled Pro Tools? etc??).

What is the exact date/model code of this iMac (from "About this Mac"/System Information utility).

Was a older version of Pro Tools installed before? how well did that work?
Did you do a Pro Tools unisntall with clean option before installing Pro Tools 9?

Did you manually install any different Digi 002 drivers (these interrupt errors are often driver problems, either bug in the drivers or the wrong driver installed) -- I don't think you should need to install separate driver updates.

What is the exact Snow Leopard version -- and how did you get to this OS version? e.g. an original install from Apple? Clean full reinstall or in-situ upgrade?

What are all the playback engine setting you have been trying to use (post a screenshot if that is easier).

Have you done every one of the standard Pro Tools systems optimizations for your computer? Do every last one however silly seeming or inconvenient, you may be able to back some out later. These get more critical the more underpowered the computer is, and yours is underpowered. All the info you need is under the "Help Us Help You..." link above.

What third party plugins are installed (if any) and are they up to date/compatible with this version of Pro Tools and OS X?

What session sample rate are you trying to work at? (Work at 44.1 KHz for now while debugging things).

Does this problem happen if you just start with a new empty session (not a copy, not from template), at 44.1 KHz with no plugins used and just create a stereo audio track and drop you favorite iTunes fie onto it and press play). If that works OK insert a few standard Pro Tools EQ and compressors plugins on that track and see if it will keep working.

I did not understand your early comment about increasing the buffer size, What you want to be increasing if needed to help with bounce stability is the hardware buffer size, (start with it set to 1024 samples). Not changing the DAE playback buffer which is what you seemed to be doing. I do want to know what you've been tryign to use before, but for now set 1024 samples, # CPU to 1, %CPU to 99% DAE Level 2. And leave those alone while tryign other troubleshooting steps.

Edit: and oh yes, is this a Digi 002 or a Digi 002 Rack?