Updating to the latest firmware and then doing a full format on an *approved* card are THE important first steps in order to troubleshoot the machine - and hopefully move on to a good experience with it.
I cannot stress this enough.... all users of the Tascam DP-24/32(SD) model porta-studios should take the time to view the Phil Tipping tutorial series on youtube. It's the difference between skinning your knees repeatedly and becoming a master of these recorders. They're great, powerful recorders (I own three) for the money.... and are incredibly intuitive once you get a grasp of the block diagram and signal flow.
You'll also find excellent support here:
TASCAM's integrated digital workstations with professional features.
www.tascamforums.com