The Co-operative Bank has been significant by it's absence from the headlines in the last few weeks. Why? Probably because it has an ethical banking policy, which curbs the lending of money to people who can't pay it back (like a couple I heard of last week, both on benefits, who were sold a mortgage which they then couldn't pay). It sounds like the Co-op is doing ok.
Given the pickle that other banks have got themselves into, and the levels of shock that Lehmanns etc. caused when they 'suddenly' went bankrupt, either some people have been incredibly incompetent, a lot of facts have been hidden from the public, investors, and staff, or people have wilfully ignored those facts in pursuit of just a bit more profit (this is also known as greed).
Where moral bankruptcy leads, actual bankruptcy follows.
Update: interesting, if slightly technical, article from the FT (HT Politics Home):
How could banks have persuaded themselves, their shareholders and the public that they were making so much money when in reality they were losing it? The history of financial deception and self-deception is as old as humanity,