trying to move a picture and I get "could not complete the Move command because the result would be too big". It is the only layer.
Seems like the file you are trying to move is really biggg!!!There is a limit of 30000 pixels on both width and height on fine and if you to File->new and create file of this size and then try to move it it would throw error.
You can just look at your file dimensions from Image->Resize->Image Size and reduce to use tht tool.