"leading Bitcoin exchange Mt.Gox "
Not since last April. http://bitcoincharts.com/charts/volumepie/ shows Bitstamp leading, Mt Gox in 3rd place. For several months it's been hard/impossible to withdraw money in USD, significantly limiting its use.
"That last point was certainly proven this week, when news of Mt.Gox's withdrawals problem sent the real-world value of a single Bitcoin – which had been stable at more than $900 for some time – into a nosedive that bottomed out at $660 before recovering slightly to around $760."
Where are these figures from? From http://bitcoincharts.com/charts/bitstampUSD , on Bitstamp (the actual leading exchange), the value was hovering around $800, hasn't been above $900 since 12 Jan.
Quoting Mt Gox prices is misleading, if you're trying to imply what Mt Gox's effect on the rest of the world was. Its prices have been inflated for months due to the difficulty of withdrawing money (so people can't actually take advantage of the higher price) - that inflation is now lost, since people can't withdraw Bitcoin either, making the price somewhat meaningless for anyone who hasn't already got money on Mt Gox (and even those who do, can't actually do anything with it other than trade back and forth). Yes, there was a drop in price, but not to the magnitude that The Reg claims. The sooner Mt Gox becomes insignificant and stops affecting Bitcoin prices for everyone else everytime it messes up, the better.