Castle reports that "there appears to be a compatibility issue between the Hint PCI bridge chip and the ALI southbridge chip ... Configuring the primary PCI bus to start up as 32bit instead of 64bit can considerably help reduce (or even eliminate) freezes due to sound loss." John Ballance said "All these mods can improve 'stability' but are not regarded as necessary if you are not experiencing problems."
The fix requires alterations to the motherboard, by fitting jumper pins and making track cuts. Some Iyonix users may be more than capable of doing the mod themselves, but we're sure Castle will arrange an alternative for those without the equipment or confidence.
Update: Stuart Tyrrell Developments and Simtec have responded to calls for assistance. For £50 (excluding carriage) they will test, strip down, modify, ressamble, and test your Iyonix. Machines may be taken (after making prior arrangements) to Simtec's offices in Preston. Meanwhile Castle have said that any machines passing through them will be modded for a much more reasonable £0; it's likely that we'll see other dealers making arrangements too. It seems that finding someone who can conveniently fix your machine, and how much you'll pay, depends greatly on your location.
Links:
Motherboard modifications
Iyonix review
Update: STD/Simtec's offer