This syndrome is very common here in Brazil with the use of crappy chips, although it does happen very rarely with unmodded stations too. The real cause is yet unknown.
The problem is in a resistor bank located in the back of the mobo close to the IOP. There are 3 resistor banks of 8X43ohms. One of them is ruined, problem is if you measure them from side to side they are ok, will read 43 ohms. You should check them side by side, they should give a very high value between resistors. Any low value or short, and you should replace that bank.
Hope it helps
At my signal...unleash hell