Can you provide a little more info on when you're calling:
Code:
Table.getTable("key").putnumber("X" , -1);
And a description of the hardware setup might help too.
Just a guess without knowing a little more about your situation...
When a target is in the view of your camera, are you flooding the dashboard/robot with data? The video freezing on the dashboard is indicative of something between the camera and dashboard getting real busy. Again, just a guess.