See this thread, and download the latest release binary:
NRage Input Plugin V2.00 BETA
Make sure your keyboard is not set up in "Absolute" mode; if it's set like this, pressing keys will move the virtual analog stick and hold it in position. For example, if you press the key for UP, the stick will slowly move up. When you release the key, the stick stays in position. To move it back to the centered position, you have to press DOWN. This usually isn't what you want, so untick the boxes marked "Absolute X" and "Absolute Y" in the keyboard setup area.