Funny thing that you mention the preasure thing and batteries. This would explain something that happened to me a year ago. Standing in the customs hall of YYZ, I turned on my phone and it started to smoke and got real hot. I figured that I had had a catastrophic failure of the battery. I never thought that maybe the preasure changes from the flight may have caused the failure.

As for the poster with the Sanyo phone, I am going to check with a friend of mine at Sanyo Consumer Electronics, to see if this has been a problem they have heard about. Only one question, are you using the original battery, another Sanyo battery, or an after market battery?