In all honesty, I've been reading about this for a short while and I don't understand. But I'm not sure that matters at all.

It seems there is a general agreement that there is a flaw in the Bitcoin model which means that in a circumstance of an organisation gaining 51% of the computational power (as just happened) the entire currency is compromised.

This is doubtless just another glitch as we progress to a crypto-currency but in the short-term, it really doesn't help.