Ultra CompactFlash 8GB

I have a SanDisk Ultra Compact Flash 8GB. I use it to record the sound that comes through the sound system for sermons. One week it will work just fine and the next it won’t. When I put it into the recorder it shows that it is recording fine. But when I put it into the computer to access the sound file and put it into a video it shows that there is no data and when I try and play it it comes up with an error message saying the player does not support the format. I have never changed the format of the card or how the sounds records. Like I said one week it works just fine and the next I get nothing.