Are you by chance loading an lsxcommand at the same time? If you are, try using a different label name. The "Command" prefix is used by lsxcommand and could be confusing things.

Also, note that the actual editbox will be in the top half of that label (it won't cover the label's height), since you're not specifying a font size or editbox padding.

I tested that without loading an lsxcommand, and it worked perfectly fine for me.