Monetary policy can have a powerful effect on the general environment, but it cannot hope to fine-tune the quarterly or even annual path of aggregate demand. At the present time we judge monetary policy to be doing the things it can reasonably be expected to do in the circumstances we face.
In part, that seems to be due to investors becoming less confident that they can base decisions about exposures to complex credit portfolios on rating agency ratings; this is akin to lenders deciding that their monitoring of risk was less good than they thought.