Hi RTT:
I enclose part of Adobe's answer.
There are two types of rich media in PDF files - "legacy" and "Flash". Legacy media is the type created by Acrobat 8 and earlier, and hands off the playback of the video or audio to an external application such as Windows Media Player, Quicktime, etc. Flash media is the type created in Acrobat 9 and later, and uses the embedded copy of Flash Player in Adobe Reader 9/X and Adobe Acrobat 9/X - it NEVER uses an external application, and NEVER uses the external copy of Flash Player you have installed for running SWF content in your web browser. The embedded version is different, intentionally so that it can block certain types of local and network access which could be used for malicious purposes.
Creation of legacy media was possible in Acrobat 9, but has been removed from Acrobat X. Playback of legacy media in Acrobat/Reader 9 and later is disabled by default, so the user must actively choose to run the content by clicking the document message bar, and/or setting trust options.
The fact you're getting a JavaScript alert indicates the media is being controlled by scripting, and if legacy playback is disabled those functions will not work, hence the errors.
Adobe strongly advises all PDF authors to use Flash media in their PDF files. Legacy media not only suffers from issues with unreliable playback on different computers, but it has a number of known security holes which cannot be entirely closed and have been actively exploited to distribute malware. This is why support for authoring legacy content has been discontinued, and legacy playback should only be allowed in files you completely trust.
So what Adobe is saying is that Adobe Reader uses his built-in player, so if I set Multimedia Trust to allow always only Adobe Flash Player (Three others to never), it should work. But not in my case. An although I set this, each time I open de file the above bar appears asking if I trust.
It's not clear.
Regards
Gustavo