EA Active has issues. It freezes frequently when starting the game, or (worse) after one has completed their workout, but before it can save the results.
My wife enjoys using it when it does work, but its very frustrating for her when it does not.
On EA's forums, many are having these same issues, but the only answers forthcoming from EA are to make sure the disc is not scratched/smudged etc and make sure no un-official peripherals are attached.
There are other issues with the game as well, so if anyone is considering a purchase, I'd recommend looking at EA's forums first.
Some people on the forums have replaced their copy 3 or more times with the same results.
no other games we own have any issues (we own 98 titles currently), so I doubt that it is the Wii itself at fault.