Just experienced the same problem last night! :-(
I heard a subtle *chaff* sound and my Amiga 1200 reset by itself. Unlike Daniele's case, i don't see anything burned. But exactly as Daniele said, my Amiga doesn't boot anymore with the IDE-Fix adapter plugged in. With or without the Express.
The warranty is still valid. I contacted AmigaKit about it and he told me to send him Both circuits for inspection, which i will asap.
If i remove the adapter and connect the IDE cable directly to the port of the motherboard, my Amiga boots as normal! It was logical to assume that the IDE-Fix adapter went bad, but from the Daniele's report i see that it could be the Gayle chip?!!
How can i see if the Gayle chip is ok or not? What are the symptoms of a defective Gayle chip? As i said there is no visible sign of damage. Please let me know! :-(