"Disk Busy" Sounds like a CPU issue to me. How much were you doing at the time of the message? It's possible the keyboard's CPU got bogged down (simply a hardware limitation). Some of the previous PSR's had lag issues from time to time due to CPU overloads.

It of course could also not be hardware related, and possibly be something that's fixed with a simple OS update-hard to really say as the issue needs to be reported to Yamaha so they can isolate teh problem (do the 900's have updateable OS's)?

[This message has been edited by squeak_D (edited 07-30-2008).]