Daniel, I’ve just had a similar problem with a Transcend 16GB card. I brought in actors and actresses from many miles away for a low budget feature to a hired location. On day one everything went smoothly. Shots look fine, day two first part of the day no problem either. Changed card when the first was almost full and I carried on shooting.
We worked through into the evening and stopped for a while. Watched back clips and everything looked fine. Set up for the next shot, switched the camera back on and proceeded. The camera was clocking up the minutes in the viewfinder then suddenly in the middle of a shot the dreaded Check Card message came up.
I shut down the camera for a minute rebooted and same message appeared. Switched off, took card out reinserted it. Same message. Tried again and again with a rising sense of panic. Had to then make a choice, continue with a fresh card and HOPE to recover the clips later or stop and reshoot but be hopelessly behind schedule (we only had the place for one more day – and people had to be elsewhere after that.
I put a ‘fresh’ 16GB card in, and continued into the night. Next day (well actually same day!), continued on with third card which was still working OK.
Got home and was able to back up everything from cards one and three but the one in between is still not recognised by the camera or any PC that we have. Following guidelines I had previously formatted the cards in camera. I then recorded on each each to capacity as instructed on the forums then deleted the clips ready for use on our feature.
The card is in for possible data recovery at the moment and I’m scared. I really like my HMC camera but I can’t shut the thought out that I nearly bought the Sony Z5 instead with built in back up. I keep wondering if I did something wrong but I used a high capacity genuine Panasonic battery and the new card ‘died’ mid-shot. I was very gentle with the SDHC (it had only been used once before – to maximum.
Searching around I quickly learned that many others have had problems irrespective of which brand card was used (this afternoon I read of someone with the same problem – using ‘extreme’ Sandisk 16GB cards).
I don’t know what the answer is. Is it the card or is it the (fairly new) camera? I noticed that as the cards filled up, then it took a LOT longer to access a clip in the ‘play’ mode. Painfully slow.