It's little confusing, are you trying to save an activity rule with name "PostActionSaveAs"? Or as in the picture attached, you're trying to Save As a report definition. Please provide a little more description.
Also, share the tracer file capturing the reported issue.
It had happened some time for me as well, but usually logging off helps. Though, please verify that the ruleset version you're trying to save is open and doesn't have the password.