Can you format it with the camera? I read an article somewhere that said you generally get the best performance out of the memory cards when they are formatted in the device they are going to be used in, rather than formatting them in a card reader.

How old is the card? They are only rated for so many read/write operations, so if you've had it a few years, and used it loads, then maybe it's reached its MTBF time. I know that doesn't help you very much, but it might be something to consider.

dont think they can be "formatted"
it's just the same as normal ram. formatting for lack of better term is done on the fly. odds are a few blocks are bad

Well, I won't pretend to know exactly what goes on when you format these things. I guess it divides the memory in little sectors, and possibly marks bad any duff ones. But you can format them, and it does delete all the data on the card when you do it.

As to their lifetime, I think they average around 100,000 read/write operations. It sounds like a lot, but I guess you can easily rack that up over a 3 year period, particuarly if you take your camera most places you go and snap at lots of things.