While working out the system stops frequenty.

I've just spoken to nintendo about the same problem. I was using rechargable battery pack. They say the problem goes away using regular batteries. I'm going to try that.

Note that the sensor bar does not interact at all with the Balance Board. It seems that you may have a defective unit. Since you have tried brand new batteries, my suggestion is to open a ticket with Nintendo through their website.

While this may not be a 100% solution, i think i can narrow it down for a lot of people. i experience this often in WiiFit... and, as others have stated, the most common time it is seen is during Rhythm Boxing.

Let me ask you folk... do any of you have your Wii Board placed up on another object to get a better work out? (If you haven't tried that, by the way, you SHOULD if your body can handle it... it turns the Step and Boxing exercises up to a whole new level!)

I work out this way... most folk i know have found Step Aerobics boards at garage sales and the like. I haven't come across one yet, so i just use bricks. Still... my board is elevated. I'd bet that other folk who experience this problem also have boards up on something (even if it's just the "feet" that come with the board)

I've observed carefully over time and found that the problem isn't random at all. It always happens when i'm stepping on or off the Wii Board, often when i'm doing so quickly or shifting from one foot to the other. The problem is always accompanied by a rapid blinking of the indicator light on the Wii Board for 20 seconds, then the board powers off.

I'm willing to bet that we're causing some sort of error mode in the device... and while i can't speak with authority, i'd bet that the four sensors in the board are only designed and rated for VERTICAL stress. If your board is off the ground (like mine) and you step on or off with too much sideways force (or front/back force) this may cause one or more of the sensors to go whacko.

Try this... try to be VERY deliberate when stepping on or off the board, making sure your weight is centered directly where your foot is being placed each time. Make certain as much as you can that you are stepping directly down onto the board and leaving it again later in smooth, even movements. I think that LATERAL stress of any kind on the weight sensors is what's causing this problem.

The WiiFit program saying "communications have been interrupted" is just how it manifests in-game, since the error mode breaks communication just as if the Wii Board had the batteries fall out or something.

I've tried to be more deliberate in my foot placement and step technique and it has helped. It's also made me more mindful of my balance and stance, which is a big factor in WiiFit in general. :-) Nonetheless, it's still damn annoying when you get the error in the middle of a boxing routine and by the time the system recovers and you power the Board on again you've totally lost your place in the pattern. That always kills my score.

P.S. - heh, what's the highest score anyone's gotten personally in Rhythm Boxing? i broke 1400 one time (i think i got a 1430-something) but a lot of that depends on what patterns you get during play. The step-back-tripple-combo is the best for high scoring by a large margin. ;-)