Several users have reported having problems saving after upgrading their game to 1.2.0. If you fall in this group, please read below:
An uninstall/reinstall of the game is reported by others to fix the issue.
Uninstalling/reinstalling will not cause your progress to be lost, provided that you have an SD card installed. You can verify the backup file, robo_defense_full.bak, is present on the SD card for extra caution.
Uninstalling/reinstalling will not charge again you for the game - the purchase is tied to your user id.
We think that the issue may be a side-effect of turning off copy-protection for the full version of the game in 1.2.0. We have wanted to do this for a while because it reduces the download size and makes the game compatible with more phones. The market tools have historically not allowed protection to be disabled; recently they changed the tool to allow it. We don't plan on turning copy-protection on again (ever) so this should be a one-time issue.