Logfile (without --debug) here:
https://dl.dropboxusercontent.com/u/44240170/logfile-fff.txt
OK, done. Aside: The previous overnight run of 3.5.1 went for 14 hours, no faults.
Started cgminer-fff again. After about 3 hours I got several LEDs full on for a few seconds. Two of them went out and resumed mining but the 3rd appeared in the display as a zombie. I was sitting next to the PC at the time, so turned on debug straight away. I left it running for a further 5 minutes then stopped it.
Logfile here, but I suspect it's not going to help:
https://dl.dropboxusercontent.com/u/44240170/logfile-fff2.txt
And...... Back to 3.5.1 again :/