Can you post a log the next time it happens?

Log cat indiates:
06-03 19:22:00.468: E/BaseCameraAdapter(1523): Ln= 744: sendFrameToSubscribers - No subscribers. frame type=1

The message shows in the ALL messages part, not the Framemarker part

There is another one which pops earlier than the previous one:

06-03 20:39:28.773: E/AR(17619): CameraDevice::getCameraCalibration(): Failed to get camera calibration because the camera is not initialized.

Ah this is so annoying! There is once the program keeps running for over 10 seconds, and the teapot indeed shows as it should be, but the screen freeze again! Anyone having any clue?

Changed to a HTC Whildfire phone, all problem gone.
Moderators you really need to have a look on Samsung galaxy s2

Hello pushi7,

Thank you for your compatability report for the GT-I9108. The GT-I9108 is a special model of the Galaxy S II build for China Mobile and has some changes from the other version of the Galaxy S II which do work with Vuforia very well.

I have made some changes to the settings for the GT-I9108 on our servers. Can you please try uninstalling the vuforia app completely on your GT-I9108 and re-installing. Please make sure you have an active network connection when runnning the app. Let me know if it works better now.

Thank you,

-Peter