Last night we had a discussion on a Rules Interpretation that was a
new one on me.

One person believed that casting a Ray Spell when in a threatened
square (even if you successfully cast it defensively) triggers an
Attack Of Opportunity.  Everyone else was going "WTF?" when this came
up.

The majority opinion was based on the rules about casting a spell -
that all actions that are part of it (including aiming the ray and
sending it off) are covered by Casting Defensively section in the PH
p. 140 ("You may attempt to cast a spell while paying attention to
threats and avoiding blows.  In this case you are no more vulnerable
to attack than if you were just standing there, so casting a spell
while on the defensive does not provoke an attack of opportunity.").
Much the same thing is said in the PH on p. 170: "CASTING DEFENSIVELY
- If you want to cast a spell without provoking any attacks of
opportunity, you need to dodge and weave."  Both sections mention the
need for a concentration check, but nothing indicates that casting
defensively doesn't apply to the entire process of sending the ray off
on its merry way.

The minority opinion was that there were, in essence, two separate
things going on.  There was "the casting of the spell" (the V,S,M
stuff) as one part  - and then there was "the aiming of the spell and
sending it on its way" as a separate part.  It was noted that aiming a
ray is likened to attacking with a ranged weapon (PH p. 175 - "You aim
a ray as if using a ranged weapon") and that making a ranged attack is
a distracting action (PH p. 137 - "Casting a spell and attacking with
a ranged weapon, for example, are distracting actions" and PH 141,
table 8-2, standard action "Attack (ranged)" has "AoO = Yes").

Under the minority opinion, then, if NOT casting defensively, you
would be doing 2 actions that both provoked AoOs (the casting and the
aiming) and someone with Combat Reflexes could try to hit you twice.

The majority opinion was used for the night to keep the game from
bogging down - but it was left open for additional input to be brought
in (Errata, FAQ, opinions of various other players/DMs, etc.).  Since
the minority opinion belonged to the DM, I thought it worth asking
about here.