The person who answered you first has one reason why it might not work, OR be erroring.
That is only half the reason to the same answer. If someone messed with the SPECIFIC DOWNLOAD SITE OR LINK you downloaded from is possible they did not make sure it was a fully compatible splice or made an error in the splice.
The other reason could be that your download site or link has been corrupted, and you should use another site or link, which is the one answer to both problems here.
The other reason my be because you have A FREEWARE that wasn't meant to let you save. Some of these FreeWares are only meant to give you a little taste but you cannot do certain things unless you download a paid version.
What do you do about it?
FIND THE CONTACT US AREA AND CALL THE NUMBER. Ask the people on the download page, or the SAI PAINT TOOL, site itself, what they think the reason is. If it is not either of the problems above, then there is something going on with your computer during the download.
Doing a System Scan, checking for viruses, and problems; also just cleaning up your hard drive will make your processor work better and faster. Along with the scan that adds to efficiency of your system is running the Clean Up too to DeFragment your Hard Drive.
You want to uninstall your SAI PAINT BEFORE YOU CHECK YOUR SYSTEM.
Do your Virus scan first. Then run it again. After that run your Clean Up and Defrag.
Try the download again after that and follow any instructions that the HELP people gave you and then see if you can save.
Please come back to explain what was wrong and what solution worked for you?
If you are told it is none of t