I have a HR44/500 with 0x797 and never had any freezing until yesterday. I had two instances of the screen turning all one color and freezing for about 10 seconds and then started playing again. Then later the picture would freeze for a few seconds and then start playing again. The last time it froze it didn't ever start playing again and would not respond to the remote so I did a red button restart.
So far it has not frozen since the restart.