Sorry for the lack of news, I was really hoping we'd have a fix for you this week, but it isn't ready yet.
To make things clearer, there are two separate (but perhaps related) issues here:
1) For most people, the video typically works on a fresh launch of the app (that is, the app isn't being restored from the background). It usually works when the app is restored by holding the home button and selecting it from the recent app list. It sometimes fails when the app is launched from the app list on the device.
2) For some people, the video never shows in the background (the background is either black or filled with visual artifacts). This includes a fresh launch of the app from Unity, even after a device reboot.
In either case, there may be an occasional hard crash of the device, especially on Android 2.2 devices. This is a well-known "cpu pegged" bug, and you will see that message over and over in the log output.
I'd like to get a sense of how many people are experiencing the second issue (no video at all), and what devices / OS version they are using. Also, if possible please send us the logcat output for a clean run of the ImageTargets sample app (included in the AR Unity Extension package on our website). You can send the log output in an email to this address:
Sorry for the delay on a fix, hopefully we'll have something next week!