The Bitcoin didn't keep its value above $400 very long, as less than 24 hours after it was trading at around $405-$420, it has lost value again. The Bitcoin is currrently trading at around $380, which means it has lost upwards of $40 in value, equal to 8-12%, in less than 24 hours.
The dive in value is most likely due to the trading activity increasing significantly on Monday, after laying low in most forex exchanges over the weekend. Unfortunately this means that there will be massive swings after most weekends, this time not in the favour of those already holding coins, but only in the favour of those buying it.
It seems that there's not much more to do to try and stabilize the Bitcoin value above $400, when considering that the year has been full of positive news for the Bitcoin and cryptocurrency in general. Maybe it will change in 2015, with a fresh new start and new companies integrating the payment method.