Found it :

.ui-jqgrid .ui-jqgrid-hbox {
    overflow:visible;
}

I have a strange problem with vertical scroll bar.
It works fine with Firefox, not with IE.
In IE, the scroll bar makes all columns not aligned :
When I use the horizontal scroll bar the column headers don't move perfectly with the rows of data.

I'm using version 3.8.1.

Thanks.

This is a representation of what I've got (X represents the vertical scroll bar).

Firefox :

Header 1 | Hearder 2| Header 3|   |

Cell1       |Cell 2       |Cell 3      | X |

Cell1       |Cell 2       |Cell 3      | X |

…

With IE, I've got somethin like that :

Header 1 | Hearder 2| Header 3|   |

Cell1   |Cell 2     |Cell 3      | X |

Cell1   |Cell 2     |Cell 3      | X |

…