I have this as a back up unit to my 797si. when purchased it would not come on just a blue screen. had sent off to humminbird and reflashed and returned for a small fee. well this unit still has not been used. went to put it on this week to try something diffrent and blue screen again. tried to hook up to computer and it wont find it. any advice, really dont want to send it back to be reflashed and have to pay again.