Comment 13 for bug 364292

I can still reproduce this with a current daily karmic.
So I looked further into the issue and here is a simple patch that fixed it for me. I'm not familiar with the ubiquity code, so this is probably not the best way to fix this.

Here is what happens:
Near the end of "set_autopartition_choices" there is a call to "self.on_autopartition_toggled", which in turn calls "self.on_extra_combo_changed". There the warning gets hidden.
Back in "set_autopartition_choices", there is then a call to "self.autopartition_choices_vbox.show_all()", which obviously results in the warning sign being shown again.

(Therefore the warning will actually be hidden if you select manual partitioning and then switch back to the first option again)

I hope my description isn't too confusing ;) but the attached file should pretty much explain it.