The Economist magazine had an article on the Nigerian economy today.  They had this revealing excerpt:

Yet even if the global crisis has not hit Nigeria as hard as elsewhere, it is exposing some unresolved problems at home. Take the banking system, which Mr Soludo says would have collapsed months ago but for an early round of government-driven consolidation. He calls the banks “shock absorbers” for the economy. But they look increasingly wobbly. Despite claims that they are well capitalised, with generous capital ratios of 22% said to be typical, they have all but stopped lending to each other or to local firms, especially smaller ones.

Critics say the banks are frozen because many are dangerously exposed to the stockmarket slump, after rashly securing a large portion of their loans with now almost worthless equities. Without government support, some banks would almost certainly fail. None trusts the others.