I've just replaced the PSU with a spare I had laying about (dont 
particularly trust it mind) and I'm no longer seeing any odd messages, 
so it *may* well have just been a dodgy molex connector. I suppose it 
could have been heat related, or something else that happens over a 
period of time, so I shalln't get my hopes up just yet. I'll have to 
give it another week or two before I am happy. I find it far too odd 
that it'd run perfectly fine for 7 days, and then these errors would 
just suddenly appear!

Something tells me it would be quite a smart move for me to rebuild that 
disk from the other disk in the array, just to make sure :)