I notice that some Matrix Infinities could not be installed in a V12, but could installed in V3-V11 without problems.
Here is the answer from the Matrix Team:
"As for the Problem with the V12, some V12 was giving some power supply instability, and to solve this issue we released last month a new revision of the Infinity, with new PCB and New code for Actel.
This Infnity have an ORANGE dot on the Actel chip instead that a blue one.
If the infinity you have are blue, than you are facing a power supply instability issue on the V12.
To solve this issue, remove the +3.3.V on the PS2 motherboard and rewire it according the enclosed diagram.
Be sure to place the diode in the correct direction.
This will solve all the issues. "
Attached the diagram.