I've heard rumors about plasma problems above 5000 feet MSL (mean sea level). Not sure what they are and if the rumors are real or even perhaps old problems that have
been resolved. Anybody have any comments on the subject. I have to do a job a little
above that altitude (between 5000 and 6000 feet) and need to know if I shouldn't do
plasma.

The pixel gaps in the panels actually seperate a tiny bit extra from the lack of air pressure, and that causes buzzing.
[Link: plasmavision.com].

According to that link, Fujitsus are rated to work without problems up to 6,600 ft.

Zenith used to make high altitude 42" ED model that had an extra "H" at the end of the part number (Z42PX2D-H). I don't know if LG has a high altitude model that replaces this old model.

Call the vendors you already deal with to see if they recommend their panel at the altitude of your installation.

I install Fujitsus and Pioneer CMX's with no problems in Denver and surrounds.

We only installed NEC's initially because they were the first warrantied to 8500 ft.. Now most main stream plasmas work fine at altitude.