Hi Andy,
From the NCH Support Team:
This only seems to be a problem with Lion (10.7.x).
It seems that MAC has triggered a security feature in 10.7.x that is supposed to only be in 10.8 called GateKeeper.
GateKeeper is set to not allow non-app store or unsigned apps from launching.
Here is a fix:
Gate Keeper settings are in System Preferences > Security & Privacy - make sure it's set to Anywhere.
This should work for most, but it seems not all.
If this doesn’t work, the MAC user might have to open a terminal session and run the following command:
sudo spctl --master-disable
and that will disable gatekeeper in 10.7.4.