All the documentation that I can find does not show if is going to damage or not the system if the jumper is off.
But I will send the information to engineering for further information.
I will be in contact with you as soon as I get more information.
The jumper-off technique worked for a while, but the startup became worse and worse. Eventually there was only an obscure message, such as "insert bootable disk", even before the F2, F7, F10 dialog came up. Finally, no POST of any kind. I played every kind of game previously suggested in this forum, such as removing the board from the case, changing PSU, one stick of memory, etc. Obviously something on the board has failed, perhaps the BIOS Flash ROM.
A warranty replacement is in process, so this issue has become moot.
Just as a follow-up to fully close this issue. I received and installed the replacement board. Everything works perfectly. The board was the *only* change, so I am pretty sure it was the sole cause of the failure.