Move along, nothing to see here!
Going into safe mode is nothing unsual for spacecraft. In a harsh radiation environment, they're subject to frequent "single event upsets" (SEUs). Well-written flight software detects these, and either repairs the damaged data if possible (by "voting" between redundant copies), power-cycles the affected system if not, or - in more substantial cases - having the safety processor drop the whole system into safe mode, from which the subsystems can be brought up, one by one.
As I think I predicted in an earlier posting here, the Sun's rather weedy "solar maximum" in this 11-year cycle has turned into a double-peak, with a lot of activity in the past few days. Click on this link to see an animation of the GOES X-ray images for the past 24 hours. It's quite impressive at the moment.
I wouldn't be remotely surprised if Juno hit the edge of a small solar storm and was briefly incapacitated. I'd be astonished if it was due to the efforts of the radio hams saying "Hi!", though!