I had the Christmas tree mung up some of my Zelda targeting one afternoon (tree is about 4 feet left of the TV). It also happened on the Wii menu. If found that if I put my hand between the wiimote and the tree, pointing was perfect. But, if I needed to get to something on the left edge of the screen, the cursor would blink on and off and appear at random points on the screen until I pointed it away and got it recentered on the sensor bar. Moving the sensor bar to the right of the TV helped with that...
I've heard (not tried it, though) that the tree lights will show up on the wiimote sensitivity settings screen if you point at them.