From the SRD
If the familiar dies or is dismissed by the sorcerer, the sorcerer must attempt a DC 15 Fortitude saving throw. Failure means he loses 200 experience points per sorcerer level; success reduces the loss to one-half that amount. However, a sorcerer’s experience point total can never go below 0 as the result of a familiar’s demise or dismissal. A slain or dismissed familiar cannot be replaced for a year and day. A slain familiar can be raised from the dead just as a character can be, and it does not lose a level or a Constitution point when this happy event occurs.
What it doesn't say is anything about level loss. XP loss from crafting doesn't cause you to lose a level but I can't seem to find anything regarding it otherwise right now. Does anyone know of a RAW answer to this or other examples to use for RAI precedent? RAW is preferred if possible.