Ok, so I pulled the SD Chart Card and the unit boots normally. I powered down and then re-inserted the chart card and it booted normally. This is a 1944C/NT display unit (purchased in 2007). Could it be related to the transducer swap out I just did. About a week ago, I had my B256 transducer replaced with a brand new B258. The depth sounder has been glitching ever since install. Depth readout sometimes disappearing from bottom right corner, intermittent erroneous readings (eg showing 3,000 feet in 12 feet of water), vertically shifting display of bottom. Is it possible this new transducer is causing a software crash of sorts?