My iPad's accelerometer is not working !!!!

I just finally got my iPad ( 32go ) really impressed and pleased so far ( it's been about 5hours...)
Now all of the sudden my accelerometer is not working any more, it's really annoying, since a lot of apps use the portrait mode really well.

Should I worry ? I tried turning it off, sync it again it doesnt work...

Did I change a setting without knowing ?

Anyone had this yet ?

....Help my brain not to worry please

Well, now I feel stupid...
I'm laughing at my self...

Thanks a lot : )
I guess I played too much noby noby boy and it drugged me