I have a FM-4850. VHF, ver 0550258-01.01 with a HS4800 handset. Part of a Nav Net TZ3 setup about two years old. After I turn the unit on it works for a few seconds then it reads "STARTUP FAILED TURN THE SYSTEM OFF AND WAIT FOR A WHILE BEFORE TURNING THE SYSTEM ON AGAIN". I have turned the unit off and waited a few minutes and hours and turned it back on and it still gives this warning. I have unplugged handset and plugged back in. The operators manual addresses this in the troubleshooting section but no suggestion other than turning the unit off and on, which I've done every way possible. Anyone ever experience this and have a resolution? Thanks.