GTI failure

I have 2 SW5548 inverters and two GTI units for a 10KW Grid Tie system. I have had 3 GTI's fail in the past 3 years. Two of them had their respective logic board literally go up in flames. The remaining GTI intermittantly drops the AC to the inverter causing it to go into "Invert" mode, dropping the grid and not selling power. I contacted Xantrex Customer Service and was told to disconnect the GTI data cable to take the GTI out of circuit to test if the inverter had a problem. The inverter never dropped the grid once in 4 days. Where before the inverter with the GTI connected would drop the grid anywhere from 4 to 10 times a day.
I was told by Gary at Xantrex Customer Service on July 30th, 2008, the GTI is no longer available, replaceable, nor repairable by Xantrex. He further stated that this puts me "between a rock and hard place". Without a GTI in circuit, I loose typically anywhere from 10-15 percent effecientcy and the AC being sold to the grid and is full of noise.Not only that, but my grid tie Net Metering is no longer valid with Edison with the GTI out of circuit.
Has anyone experienced this situation? Does anyone have a schematic of the GTI? If I can figure out how to keep the GTI internal inductor in circuit, I can at least clean up the output AC and increase the efficientcy of the grid tie sell back or replace the relays if that is where the drop out is originating from.
After being informed about the GTI status by Xantrex, I wonder if in the very near future when these things start crapping out, are those of us who invested thousands of dollars in Xantrex products going to have to replace these inverters when they fail since it is obvious that by the action taken by Xantrex, the SW series inverters and GTI units are doomed.

That would be great to know. Thanks very much