Ok first off please post a copy of the log from ImgBurn, that is all the information that appears in the bottom window under the main GUI. That will tell us a bit about the media and its supported write speeds - I am guessing that yours does not support 1x and probably has 4x as the lowest.
As for closing, I think you can do this with ImgBurn open, select the Tools menu and it's one of the options there - you may need to close track before disc if that's available to you, sorry never had to do it manually myself and my memory of reading this in the forum is a little foggy.