[MacBerry]

Where are you creating it? If you're using quick entry, then you can check the "Immediately clean up quick entry items" option in Preferences>General to make it do what you want.

If you're entering the new items "inline" in the inbox, then you have options: either click on clean up on the toolbar, or hit cmd-k, or drag the item to its (already assigned) project or context. Just assigning the project or context won't do it, I think probably sensibly as otherwise the item would disappear from in front of you the second you gave it a project, when in fact you mat still have more editing to do.

Mark