A thought.

If you are using 1280 x 720 HD mode, there could be problems if you are not using a fast memory card.
You should be using at least a Class 6 (speed) memory card.
If not you can get dropped frames and corrupt images.

You can get speed information here:
http://en.wikipedia.org/wiki/Secure_Digital#Speeds
In the Table of Contents click on;
3. Speed.

Try taking videos at 640 x 480 and see if you get sparkles in low light.
If it works OK at 640 x 480 - go shopping for a faster memory card.

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