Filippo, that's not a bug, but it is in normal Baobab's behaviour. If you mount/unmount a device while baobab is running, the properties dialog pops up to let you include/exclude the new mounted partition.
- Bug#346368: baobab: pops up new dialogs when a device is... Fabio Marzocca
- Bug#346368: baobab: pops up new dialogs when a devi... Filippo Giunchedi