Hi All
Sony replaced the camera on Monday with camera
#110060 (an even earlier serial than the one I had issues with). They did not tell me exactly what caused the issue (I'm not even sure that they know) but the tech who worked on it said he thought it was possibly one of the camera's chips. He said class 4 and above cards should be fine for HD recording.
I have reformatted all memory chips and the FMU128. I am currently travelling but will be shooting by the weekend. Will update this forum if any problems strike again, or if they don't.
Best to you all.
Adam