I am experiencing the same thing with Super Mario Galaxy. The remote jerks and is twitchy when I play this game. When I move the remote around the screen (to pick up star bits, for example) the cursor jerks around and the wii remote rumble activates, like I moved the cursor over a button or something else selectable. Of course, nothing is there to select, it just does it randomly. Also, like the OP, it makes it really hard to select anything - when I select a galaxy or a level within that galaxy, the cursor freaks out. I can still select the selectable item but the icon freaks out, the remote rumbles constantly, like I am constantly moving my remote from and back to the selectable area (sorry if this is confusing, it's really hard to explain). Incidentally, I have tried this with two remotes, to the same effect.
I get this a little bit with the Wii menu, but it really goes into overdrive with Mario Galaxy. I have also tried Wii Sports and Trauma Center: SO, and it's not nearly as bad as it is with Mario.
This sounds to me like a sensor bar issue, but I have no other lights or IR sources (except for my cable box about 9 inches above the TV) near the Wii or the sensor bar. The only thing I can think of is that I have two glossy 24x36 posters on the wall behind me, but not directly behind me, about 6 feet either side of me - can these reflective surfaces also be the culprit?
I just got the Wii a couple of days ago, so I am most certainly a Wii noob, but I think I have done everything correctly in terms of setting up the Wii and sensor bar.
Has anyone else experienced this - I can still play the game fine, just the jerkiness of the cursor is really bothering me.
Any help would be GREATLY appreciated! Thank you!