How can I fix my Panasonic DVD Home Theatre Kit?

My Panasonic Ht-70 DVD player every now and again will switch itself off, usually whilst either reading or playing a disc. It will then stay switched off no matter what you press even though the power light is on. This usually only happens if it has been playing for less than 1/2 an hour or so, if its any longer then it is usually trouble free. Once it has turned off and 'locked' itself it will stay locked for a random amount of time, can be 5 minutes or the longest i've known it to be in this state is around 24 hours! Any help is greatly appreciated.