I think you may have made a small mistake with the code update.
Anyway, I've released 0.7RC5 now. It has a better fix for this behaviour - thanks for pointing it out!
However, what may be more interesting is the new option now:
If you have keyword and/or description generation turned off you can force processing by putting @PROCESS in the metadata box. This will then autogenerate just that box - ie description. You can then add whatever you like. Luckily, whatever you put into the keywords or description boxes manually will be preserved until you then tell AK to @PROCESS again. Nice eh?
Download it and let me know...