Comment 82 for bug 952556

I wonder why you are not using by default laptop-mode in ubuntu instead of trying to hook hdparm rules here and there.
I have switched to laptop-mode, set all values for hdparm -B to 254 and problem is gone.
I have uncommented also in /etc/apm/event.d/20hdparm:
APMD_DRIVES=""
Don't know if it is relevant.
I am using xubuntu and I have unchecked in the power manager setting the spindown option, to let laptop-mode do the job.
laptop-mode allow fine settings for many other things also, using it would simplify a lot power settings in ubuntu.