My guess is it's your PSU. The PSU is usually a part of which people don't even think that it can also be faulty. After all: it works, doesn't it? Wrong. If the voltage isn't 100% correct and stable, then you can get all sorts of weird errors. I recommend replacing your PSU.
(the PSU may very well have been the reason for that blown up cap as well)
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Riocar 80gig S/N : 010101580 red
Riocar 80gig (010102106) - backup