Here's a test cap: http://db.tt/QXvbs0 req 0.99.84 or newer.
As long as the object is flashing, trying to make the object visible or invisible has no effect. It looks like this is by design because all flash does is make the object visible and invisible at regular intervals.
I'm having no problem making the object visible or invisible once the flash is done.
Stopping the flash is fairly simple by using the flash action with just zeros:
-> Sprite: Flash for 0 seconds with 0 seconds interval[/code:1rjaxayk]
but since you said "that's not the point" I guess that won't help.
I find the way flash currently works to be acceptable, but that's just me. It's simple enough to do those actions you need done. For example to hide a flashing object it would only take two actions:
[code:1rjaxayk]-> Sprite: Flash for 0 seconds with 0 seconds interval
-> Sprite: Make Invisible
[/code:1rjaxayk]