Since electronics do not know much about elevation, there are two major
changes - temperature and pressure. The largest change would be a change
in
temperature. Unless electronics are heated, there could be a major
problem
for displays. Also, batteries may not work as well. Pressure change
should
not be much of a problem.

When it comes to radiation, the question is how long the electronics are
going to be up there? Unless it is a very long time, I doubt the
radiation
will be a major factor.

Actually it might be a factor. NASA research aircraft have had several
single event upsets in semiconductor based memories at 40,000 feet on
missions lasting even just a few hours. Avionics containing microprocessors
and memory were not affected but the desktop grade PCs strapped in equipment
racks would crap out with a memory parity error or something once every few
days. They believed it was radiation induced. The same computers worked
fine on the ground. The Kuiper Airborne Observatory (a C-141 A model) is
one example where this happened.