gdgt

If you go into the system config menus on the Wii, you can adjust the sensitivity of the wiimote. While you are on the screen, it will also show you what the Wiimote "sees". The sensor bar should show light on both sides of it.

Make sure the sensitivity is not so high as to be picking up reflections, or the power light on your TV.

have you tried moving the sensor bar? for my own setup, i had to move my bar from under the tv to either the top of the tv, or what i found worked best, on the bottom of the tv, yet pushed to the very front of the stand. about 7 inches infront of the tv.

Since the sensor bar is nothing but two IR light bulbs, it's easy to troubleshoot. Like @yimmy149 mentioned, head down to the place in the Wii settings where you can adjust the sensitivity. Make sure that you can see two dots on that screen when you move your Wii remote around.

If you see less, then one of the bulbs is either obstructed (could be too far in, and blocked by the TV) or damaged.

If you see more, it means there's something reflective in the room that's reflecting the two bulbs. Sometimes it's the floor, if it's made of shiny material like marble. Sometimes it's a glass coffee table. In really rare cases, it could mean there's something else in your room that's emitting IR light, such as a faulty TV remote, or even a lit candle. The pointer usually skips around when it "sees" more than two dots.

ya, the wii sensor is really hurt by outside light sources (especially from the same area behind or to the side of the TV) and distance and off angle play. You really need to be less than 8 feet form it and in front of it... not far to the sides where it only catches one ir bulb...