Zweistein

In my case it's when connected to external power. Doesn't seem to matter if navigating or not. Neither which profile is used. Will test more. I have never had it power down unexpectedly plugging in or removing power.

In my experience it IS a firmware issue. Since upgrading to 2.60 I have frequent shutdowns when connected to external power. I think I have found a workaround though, if I change the backlightlevel to anything but the default (off by day/low by night), it seems to stay on. Did not have this issue on 2.50. (I skipped the betas)