It was strange to me because the sound track was playing in background but applet had a problem with loading images.
Presuming the image and clip are in the same directory, it suggests the music clip is being loaded by URL
from the 'home' location (OK for a sand-boxed applet) while the image is being loaded by File
(only possible in a trusted applet, and not suitable for resources we supply for an applet).
Organize to load the image by URL, and it should work.