You know that I have remembered a very recent error, that i think i fixed with my most recent update, that someone reported was causing the same "Error on creating PNG".
It was described here:
https://www.donation...x.php?topic=45791.25Essentially it was related to compression level being set to 1.
Can you check that you have downloaded the very latest version, and check that your compression level is not set to 1 or 10 in the File Saving tab.