Banks hide their fragility and vulnerability behinds marble walls. Sometimes they hide worse things. A series of bank scandals is sweeping through much of the developing and third worlds - Eastern and Central Europe in the forefront. Many things - almost everything. It is mainly a crisis of trust and adverse psychology.
Financial experts know that Markets work on expectations and evaluations, fears and hopes.
The fuel of the financial markets is emotional - not rational. Banks operate through credit multipliers. This is called a reserve and is intended to serve as an insurance policy. The commercial banks hold their reserves with the Central Bank or with a third party institution, explicitly and exclusively set up for this purpose. The Borrower pays Bank A interest on the loan that he receives.