For people that lost their save games here is a list with different progress levels.
After downloading and unzipping the file, rename it to the slot number you want (eg. slot_3.plist is slot number 3) and move it to the corresponding save game directory:
C:\Users\username\AppData\Local\Kingdom Rush Vengeance
/Users/username/Documents/Kingdom Rush Vengeance
The achievements you have on Steam will not be back into the game, but you will not lose them.