unwanted Midi triggering

I have just made a chord progression with my Access virus A.
in the sequence a high note comes on randomly, not part of the sequence and doesn't stop playing until i reset midi panic
this keeps happening and is driving me nuts any ideas why this is happening
I have cut out the notes and made a new block.
disconnected midi out from the virus and disconnected my midi usb keyboard still no joy

if anyone could help?
thank you