The function in question tries to load a new texture via TextureManager.loadTexture from a path on the same server. This is where the exception "java.lang.SecurityException: Unable to create temporary file" occurs.
More specifically it occurs in on this line:
java.awt.Image image = ImageIO.read(stream);
com.jme.image.Image loadImage loadImage(String fileExt, InputStream stream, boolean flipped)
I've checked and double checked. All the jars are correctly signed. In the same function I also load a .obj file and this works with no issues leading me to believe this is not a security exception but something else…
I appreciate this is an odd one but any help or advice would be great,
The ImageIO class probably creates a temporary file for caching and such, this is not permitted in the applet security policy. You must disable the use of caching or creating temporary files for the class ImageIO, or use the AWT Toolkit class to load images.