I've had trouble before, after editing tracks in Basecamp, but this time, my Oregon 450t showed signs that I interpreted as hardware problems.
Screen would fade away either just after bootup, or when accessing the map.. As if the unit lost power. I replaced the batteries, but no better.
I then read the Oregon Wiki and tried the Master Reset, and the unit came back to life.
It had lost all access to the GPX files (waypoints, geocaches, etc) but I could still copy them off the unit to my PC, rename the GPX folder (just in case) and load the folder back onto the unit.
All is well now, but I am somewhat concerned that the unit can mimic a hardware power failure, when it is a software problem.. I was frankly ready to send it in for a warranty repair!
I am on release 3.71 now, should I upgrade to 3.74 (there is a mention of power down problems fixed) or stay put?