There is a small bug in DVDA 5.0b that causes subtitles on some playback devices to turn on when they are not supposed to, and which also causes any "subtitle on/off" buttons you create to not work.

It took me four hours to find this, so I am posting this in the hope that if someone else has this problem, they won't have to waste all that time.

The problem is caused by the language selection for the subtitle track. In my case, I set it to "English" and this caused the problem. Everything worked fine in the DVDA preview, but when I played it in PowerDVD, or created a disc and played it two different Pioneer set-top NTSC DVD players, the subtitles were on as the default (even though I had them off in the Properties, and had a startup script which also turned them off).

The solution is to change the language setting on ALL subtitle tracks to "unspecified."

I did not do any testing to see if this bug only applies to English, and whether it also exists if you have more than one subtitle track.

I hope this helps someone.

Oh, and FWIW, I reported this to Sony tech support (via email) and they were VERY quick in responding, and VERY helpful.