It is most probably the internal Power Supply Unit (PSU). These were built using cheap components (namely the capacitors) which were only just upto the job (ie good enough for around 13 months heavy use). There are more details
in this thread from Kafka's World here. Basically, failing capacitors mean the box is struggling to function on the wrong voltages and noisy power (crackles on the line to you and me). This incorrect and dirty power can cause all manner of random problems. The most common are failing to fire up the hard disk, problems downloading new software and problems with tuning.
There are two capacitors in particular that fail (details in the thread I linked to above). These can be replaced pretty cheaply with
far higher quality caps from Satcure that will almost certainly never fail again. If the person who bought your DTi 6300 (or a friend of his or hers) can solder repair is pretty cheap. I bought a DTi 6300 for my parents for a stupidly low price on eBay around 6 months ago. As a precaution, I upgraded all the capacitors on the PSU (not just the duff two) and the unit has been very reliable ever since (despite running 6.54 software).
