This is correct. A shield provides an armor bonus, and Mage Armor provides an armor bonus. Since they're the same type of bonus, they overlap.Dash Dannigan said:
The entry for force shield notes it works just as a normal (large) shield does, granting a +2 AC. Perhaps an individual with mage armor gains no benefit from using a large wooden shield then?
The special exception is that the armor bonus from one shield stacks with that from one suit of armor. Neither the Mage Armor spell nor the bracers counts as a "suit of armor," therefore they still don't stack with a shield.
This is in the FAQ (MainFAQv12102002.pdf, p25).
Note that even though the ring of force shield is based off the Wall of Force spell, it does not provide cover or block line of effect. Someone using the ring can still be targeted by spells normally. The only benefit he gets is that +2 to AC.