When I deposit some money into my bank account, the bank can lend a proportion of that out again. What happens when I withdraw the cash and deposit it again immediately? Is the bank allowed to lend on that again?

no effect, they can lend when the money is in the bank... for the brief moment you have the cash in your hands they bank cant lend that money out. If everyone withdraws there money at the same time, you get a bank run, and the central bank steps in my printing money/loans the bank money to bail the bank out (i.e. Thats whats currently happening, credit crunch)... Of course this is a short term measure, as printing money creates inflation....

The central banks are in control, if everyone takes money out the bank they have two options and its up to them to decide:
If they bail banks out they create inflation and debt continues
If they don't bail banks out we go into a recession or worse still a depression

Thanks. What I'm trying to determine is if they need to reverse any of the lending (somehow) when I withdraw my savings. And since they have no idea where my money comes from, and they don't need to reverse the lending, what stops them lending against the same money again?

Yes, they have to reverse their lending which was based on your deposits (when you withdraw). But in reality, your withdrawal is a drop in the ocean to the bank. All they need to do is make sure their reserves, i.e. your deposits, don't fall below the level set (BASIL criteria). If it does, it has to borrow money to fill the gap, and pay interest on that money from their profits. If no one lends to them, they have to borrow from the central bank - this is what has happened recently.

I'm sure banks have complex models which take into account a certain percentage which will withdraw that day, so they are probably be anticipating your withdrawal. Either way, what happens to your withdrawal? You put it into another bank, so there reserves are larger. They then can lend this out (through FRB) to your original bank as mentioned above.

Unless money is never paid back, i.e. bad debt, or withdrawn and put under the mattress/burnt, the banking system will survive as it all balances out. The problem is the bad debt part is getting bigger and bigger....

Thanks.

This, I think, is exactly what needs to be considered... These are my ideas:

1. What are the real losses as a consequence of credit card fraud? I personally know dozens of people who have been a victim of card fraud - yet we hear little in the news about successful prosecutions and recovery of funds. To what extent are losses covered up to avoid denting confidence?

2. Enron managed to deceive the world for a significant period with accounts that looked good, but actually hid staggering losses. Is there any way to estimate the scale of liabilities arising from creative accountancy?

There are no consequences for credit card fraud. The money was always imaginary and no loss can have occured. The credit card companies obtain their money in the same manner as all loans - they take the borrowers promise to pay and treat it as though it was money. The borrowers form is monetized -

http://en.wikipedia.org/wiki/Monetize

No idea about 2 but banks routinely put onto the asset side things what no sane human would ever dream of doing. Do you say after lending our mate Dave £50 till weekend that you have gained an asset? Nope, me either.

If all depositors withdrew their funds, all loans stay live. This is because no depositors money is lent to anyone at any point, it's just there for people who come into the bank to be given to keep the whole house of cards going and to obtain the licence from the central bank.

Think of it this way.

If northern Rock lost all their depositors, how many people would/will have had their mortgage cancelled or called in?

None.