Hi - I have a similar problem. I have a GT 5.0 inverter which was only installed a week ago. Its worked fine until now making around 18 kw per day even though its winter here in Australia right now. However today I checked it and the red "ground fault" LED is on with no messages displayed. Also knocking the panel doesn't get the light on or show any messages either...
One thing though. The switch for the solar system on the house main circuit board was turned off yesterday morning (as the electrical inspector was coming to check out the installation in a few days). Our installer told me to do this as its not supposed to be connected to the grid until the inspector signs it off, (he left in on for the first week so I would get the benefit of the system until then).
Is that why the red LED is on? Has it detected that its not connected to the grid? And therefore will it reset itself if I switch it back on, on my house switch board? (I'm afraid its night here now so I can't try that one until tomorrow).
The manual says there should be messages on the screen to accompany the red LED... Any clues?
OK - some follow up from the next day...
With a bit of sunlight the red LED has gone out and the message "Inverter off line" etc was displayed.
When I switched the system off at the house switch board it restarted and is working no problem.
So thats 1 abnormal event not mentioned in the inverter's manual; If you switch the system off at the switchboard, you will get the AC voltage fault message during daylight, but once the sunlight goes the red LED appears with no messages.
IMHO it might be worth Xantrex putting that in the fault finding section. The only reference to the red LED at present (in my manual anyway) suggests any time you get the red LED - call a technician, as its a ground fault and only they can fix it! There are numerous reasons why one might turn off the system at the switchboard, so this behaviour should be referred to, avoiding unnecessary call outs of electricians etc (in Australia you can't legally play with this stuff yourself).