strange TypeError exception in function compiled from a string

[nelson]

Hi all,
  I have this function, defined in a string and ecetuted through ad
exec call

def cell1(d):

    x=d.get('x')
    print x

    import y
    return y.add(y.add(self.adf0(x),self.adf0(x)),self.adf0(x))


d is a dict of this kind {'x':2}

I receive the following exception, that i find very strange...

  File "<string>", line 7, in cell1
TypeError: 'dict' object is not callable

I have tested all the function al line 7, and none of them raise any
exception.
Have anyone some suggestion on how to solve this?

thanks!