Nacoya,
You are correct. The Alt + Mask Click works manually but will not work in an Action. I am not sure if this is a bug or if there is a reason. It would be worthwhile posting the question in the Adobe Photoshop User Forum
http://www.adobeforums.com/cgi-bin/w...BzqJs@.ee6b366
In the meantime, here is a work around. Instead of doing Alt + Click, make sure that you click on the layer mask to make it active. Then do Image > Apply Image. When the dialog box comes up, select the background or merged RGB image which should be the default. Make sure the Blend Mode is set to Normal and the opacity = 100%. This will accomplish the exact same result as the Alt+Click+Paste.
Regards, Murray