If you are going to store data online always encrypt it locally first in your computer, never trust a third party service like Dropbox or Hushmail with your data even if they tell you they can’t access it and that everything is fine, the bottom line here is that they have access to the decryption key.
Besides the chances of encryption implementations being flawed by your online storage service, they can do anything they like with the decryption keys, if you send the data already encrypted to your online storage space you will be the only one who can decide when and how to decrypt your confidential files, you will also protect yourself from a rogue employee tempted to look at your confidential files.
PS: I am adding Dropbox to my shit list.