It might be true that some of the investment banks took on risks in ways they did not understand, e.g. default swaps and corresponding derivate, and some of these default swaps maybe still buried somewhere. However these risky assets will not matter as the Fed already is backing the housing market and there will be no melt down. Eventually these risky assets will bleed out with time, and these investment banks will go back to make a ton of money. That's what they are good at.
All investments are risky and fools will be separated from their money fast...invest/trade at your own will.