there can be many things to make this happen.
1. client is open or running when tryng to save with
reshacker.
"rarely you get lucky and it will save. other times it glitches or wont save"
2 picture is open or being used by paint/gimp or whatever you are useng to pixel.
3. window see's client gfx comeng from other source and blocked it, right click gfx folder and see if it says it may be blocked at the bottom.
them are the three top ones that i have seen to say it can not save the file.
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Think Outside The Box.
..............Skids in my Undies........
...............Cut And Paste............