Why is this happening ...
Probably is explained here:
Recent USD/BTC rate rise caused the pool's hot wallet to be drained MUCH faster than usual and I had to manually refill it. Delays up to a few hours were experienced, but I think that it never happened for a 24h in a row.
As you may know, the rate is now all-time-high, so lots of users are cashing out.
I need to transfer some bitcoins immediately ...
Your wallet at DeepBit is a hosted (shared) EWallet. What this means is that you don't have control over the coins but instead are just sending a withdrawal request to DeepBit and then they service that request.
Thus if you want the control over your own funds, DeepBit or any other hosted (shared) EWallet provider is not the place to store your coins. A local Bitcoin client such as Bitcoin-Qt, Multibit, Bitcoin Wallet for Android, or even a hybrid EWallet such as Blockchain for Android and iOS will be better options for you if you need a guarantee that you can send payments without any delay.
