It could be a "bad" card, and I use the term loosely. Memory chips and cards have a specification called MTBF, Mean Time Between Failures. What that specification tells you is how many reads from a memory location can you perform before the memory chip will return an incorrect value. A similar specification applies to writing to memory.
You might see a number that seem rather high, a MTBF rate of 1 in 100 billion. That sounds like pretty slim odds, but when you consider that the we see clock speeds today of 2 Ghz , or higher, that number looks like it could mean that you can get a failure as frequently as once every 50 seconds. Fortunately, that is not quite what it means.
The MTBF rate is actually referring to every memory location on the chip, and out of those billions of bits just one of them will report bad data, which means the oddds go WAY up in your favor because you would have to performing a read/write operation to that bad bit and that specific moment when it fails to function properly.
So, it could be a "bad" card, because it has poor a high number of failed, or failing, bits in memory. I'd say try a different card, one that is a different brand and maybe not as high of a capacity. All we want to do is test, and this test card can serve as emergency backup if your main card catastrophically fails, or if you need more storage space on a shoot. Besides, if you're serious about your video shoots, you should always carry a spare card.
--------------------------------------------------------
"Fooling computers since 1972."
