I Have Synth

Hi all.  I have an MC50 problem that I hope you can help me with.I recently started using my Roland MC50 again after it had been boxed for a while.  It's picked up an annoying habit:  It sends zero-velocity 'ghost notes' at seemingly arbitrary times when I send MIDI through it from my e-Keys 49 to my Proteus.  Here's the play-by-play: I press a key on the e-Keys, that note is sent to the MC50 and then through to the Proteus as expected.  But about 40% of the time, a half-second later the MC50 sends an identical note number to whatever note i just played, but with zero velocity.  It acts like a 'note off,' basically turning off the sound.  It happens with chords too: If I play and hold four notes, maybe three of them come out fine but after i press the fourth, zero-velocity notes are sent that are identical to all four notes and the chord is interrupted.  Obnoxious.   Possibly related:  I can play back several recorded tracks simultaneously on the MC50 without incident, but when I press an e-Keys key to record onto a new track, the MC50 stops immediately and says "MIDI OFF LINE."Has anyone else run into this?  What should I try?PS: Otherwise the MC50 behaves itself perfectly, so I have been using this as an opportunity to improve my step-record skills :)