actoolkit not letting me save my work?!

I did everything the instructions said. I opened up RVFOREST.dat and actoolkit opened. (I found it in the savegames folder) and after I finished working on editing my town and such, I clicked save. Then a popup said "Unable to save! Make sure the file is not in use by another process". It's been doing this the whole time. The only time it let me work is when I dragged the rvforest file to the desktop, opened it with actoolkit, and it let me save. But that's pointless because it wont let me copy the new file with the old one. I created a backup of my edited town, so that way when I can actually save my game, my hard work won't go to waste. Is there any solution to this problem? Please help.

If you're trying to save it on the SD card, you probably have the slide switch on it locked. Check that and try again.