Empty smart cards

I drove 2 hours to the sleep doc today only to discover that my smart card was empty when they tried to download it. This happened once before while I was still on bipap, so now this is two different data cards that have failed. I called the DME to set an appointment to come in tomorrow to see if my new card is working (she wanted my old card, too, but my doc's receptionist shredded it - dumb, since it was blank...).

Anybody else have these problems or am I just unlucky? Maybe I have a random electronic problem in my house.... who knows.

My first card would not accept any data -- they figure it must have been corrupt. I missed the first week of data. When I'd turn off my machine in the morning, the machine would "beep" in rapid succession and display a "remove and reinsert data card" announcement. It would not save any stats. I was sent a new card this last week, and so far, so good -- it seems like it's now working!