Medion MDPNA175 Crashing

Hi, I've had this unit for 3 weeks now and overall I'm reasonably happy with it but I've started to have some problems, 4 days in a row I have had a windows type dll error when I've switched it back on and yesterday in the middle of a voice prompt the unit just stopped, the screen went blank (but still on)...

on all 5 occasions it has needed a hard reset to resolve, Medion tech help have suggested clearing the flash memory, which I have done, but I don't see how this would help these problems...

any thoughts?

cheers
dee