[LAU] Sustain pedal issue with undesired repeated notes (m-audio keystation 88es + qjackctl + qsynth)

[Nicolas BERCHER]

Hi,

I have a problem I can't face alone on the digital piano I made on 
Debian Lenny with qsynth (v0.2.5-2.2), qjackctl (v0.3.2-1) and an 
m-audio keystation 88es keyboard.

When I play the piano, some notes will repeat themselves after a few 
seconds only if I keep the sustain pedal pressed, just like a delay 
effect would do.
I reported that only 4 notes are concerned for the moment, they have 
different repeat delays:
  G  : ~7.5 sec (G4)
  G# : ~7 sec (G#4)
  A  : ~6.5 sec (A4)
  A# : ~6 sec   (A#4)
Note that the notes above, relatively to the middle C of a piano 
keyboard called C3, goes from G4 to A#4.

Could this be due to an hardware issue in the m-audio keyboard?

Thanks a lot for any idea on how to track down and correct this (if 
possible).
Nicolas.