Clicking onthe refresh button on the UI builder can loose fonts and image displays that you had to start with .. and only closing the UI builder and restarting it will display them again..
Also somtimes if you copy and paste a style it will loose the first part of the path data in the window that calls it... Hence loosing the image so to speak, You just need to correct the path info... There is so many interesting quirks in the UI builder that it is hard to pin point exactly what you are trying to say lol (well for me anyways)
Also check that the style / whatever you have pasted still refers to the correct location IE you have a progress style and a progress fill, does the progress style still point to the progress fill?
Hope this of some help m8