Through the process of creating Generic Annotations for element symbols, one will commonly encounter one of the most popular error messages in all of Revit:
Upon investigation into the exact cause of this message, it was discovered that occasionally, even manually inputting a great distance when drawing or moving a line would produce this error. After some experimentation, it was concluded that this error is prompted exclusively by the proximity of the cursor from the origin point. That is, when you first click to draw a line, if the error symbol (Ø) is beside the cursor, the error will always come up even if you typed in 1000'.
In order to avoid this error, always move the cursor to the opposite side of the screen in the direction you wish to draw or move something, or at least far enough away that the error symbol is not present. You can then manual type and input any distance, so you can even move an element by as little as 1/2048th of an inch.
NOTE: This is a completely separate error from "Line is too short".