Hi,
Since Action! 1.5 I noticed a bug and I've just found how to temporarily resolve it on my system.
I've updated Action! to version 1.7 but it's still there.
So, when I launch Action!, I can see that the process Action_x64.bin is using some CPU, and won't close by itself when I want to close Action!, which makes it to crash.
The solution I've found : using ProcessExplorer I double-click on Action_x64.bin, go in the Threads tab, and then kill the thread using CPU.
By doing that, I can close Action! (and then update it when there's an update).
There may be some loop somewhere in this thread causing it not to en properly.
Here is a screen of the Threads tab in ProcessExplorer :
I'm using Windows 7 x64 (with a Windows 8 skin).