I've had a similar problem with my MC505 - Please refer to a recent posting. I've reinitialized (see manual) my device after saving my patterns on a smart media card. I do not use a computer when composing so I cannot say it is the monitor. My current feeling is the internal battery must be frizzing. So far though, it hasn't repeated the symptom. I wish I could tell you definitively that is the problem, but until I can get some one to discuss this who knows, I go with the conspiracy theory ie planned obsolencence.