Thank you Chuck for your input.
I benched tested my C90W and fluctuated the voltage during test. I found it was operable down ~10.5v then it would turn off. I took it up to 14.75 with no problems.
Any idea what fails on the course computer? What are the usual symptoms?
Try the test with the backlight turned down to a nighttime setting. My Raymarine E Series units are not stable when you do this. It is as if they amplify any line voltage fluctuation as changes in display brightness. At full illumination either the changes are too small to see or they go away. Raymarine tells me that the illumination circuit is the first place any voltage fluctuation or interference shows up, they recommend a 12vdc to 12vdc Master Volt as a power supply to cure the problem.
To update my previous comment about RNS software:
RNS software version 6.1 and E Series firmware 5.52 are happy together! RNS seems to run just fine on Windows 7 with no need for the XP virtual machine. I don't have enough time on the system under Win7 to know if it is 100% compatible yet, but the Vista <> SThs problems seem to be solved so far.