Just as title said, basically what I did was create a new group where dithering support would go, and the instanced layer of that group are created on the older filtered image group. The older filtered group now has filter layers. Here's the kick, you are no longer able to save the document. I suspect that the rendering takes forever on the background, and unable to cancel.
I found out that you can create a copy from current image, and then you can use save as, and it'll allow you to save from there.
Can you either share your file with us or give us an exact description of the layer stack and other document properties? As is, it's completely unclear to me what you're trying to do.
It's no use having two reports about the same file. *** This bug has been marked as a duplicate of bug 387267 ***