Two things:
1. The first PSR-S900 had problems right out of the box before I plugged the midi device in.
2. The midi device only does one thing: It sends a message to sustain notes on channel one. It shouldn't be causing the Music Finder database to come up when I press variations C & D.
3. I did a full system reset and the problems persisted. I cannot see any way that my midi device would have caused a hardware problem or a software problem that could not be resolved with a system reset. I was able to get OTSs #1 and #2 to start working again.
4. I have been using this device successfully with two PSR2000s, two PSR2100s, and two PSR3000s. Outside of the Data Select Wheel not working with one of my PSR-S900s, the keyboard is stable using this device.
5. Sweetwater Sound had a PSR-s900 before almost anyone else had one. I was one of the first in the USA to get one. I doubt it was a return or refurb.
6. The latest keyboard I got was shipped the day it was received from Yamaha.
All that said, I do regret not having bought my keyboard from George.
I seem to have bad keyboard karma.
Sweetwater is going to test their one remaining PSR-s900 before they ship it to me to replace this one.
Beakybird