Hi Iain, my name is ***** ***** I will do whatever I can to help answer your question.
Before I start researching the problem I'll need a few important details.
Which version of Mac OS X is on your iMac? Can you click the Apple menu - About This Mac - and give me all the details of your system from there. What version of OS X, what processor and how much RAM.Which Pro Tools hardware are you using if any? Can I have the make and model number and the connection it goes into on your Mac.What are the steps you take before the error appears, and what is the exact error message that appears?
Thanks in advance,