if its a cheap no brand card they tend to fry and loose footage. i had a cheap card that was supposed to be fast enough for gopro but it fryed and lost a bunch of footage. try a name brand card with a good class rating and see if it works better.
never heard of maxflash. gopro has a list on their website of known compatible sd cards. it could be something as simple as the contacts being dirty. does your camera still read the card? does your computer read other sd cards? try both of those to rule out a problem with either the camera or your computer. then see if another computer/reader can read the card.