I sent this in to Humminbird:
This is reporting a software problem. I am running software version 6.640 on the 1198c SI, and I have the XM weather accessory.
From the Views Menu:
If you set the split screen Chart/XM Weather View to Hidden, then scroll through the views and get to the XM Weather View, the Chart/XM Weather view willl re-appear. If you go back to the Views Menu, the Chart/XM Weather view will have reset itself to Visible.
This also happened on my 1197c SI with software version 6.310.