UPDATE:
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I have just found that the screensaver actually crashes our app even when it's not playing anything. I simply opened the app and waited for the screensaver to turn on. When it did, the screen began to flicker (alternating home view and screensaver). After pressing the home button on the remote, the screensaver froze. Pressing another button dismissed the screensaver and showed that the app was no longer running.
I then discovered that the sample "audioapp" also suffers from exactly the same problem:
1. I side-loaded the audioapp sample (without making any modifications to it). After the app started, I left it in the initial screen. Debugger output so far:
------ Running dev 'Audio App' main ------
Entering Main
Saving Cover Art URL: yoyoma
Enter PosterScreen getsel
2. I waited for the screensaver to turn on. At that point, the debugger reported an event:
posterscreen get selection typemsg = roPosterScreenEvent
then the screen flicker began, and the screensaver started. After pressing the home button, the screen saver froze. After pressing another button, I could see that the app had died.