Okay,

Base is 10
Add 4 bonus for 18 Dexterity, now AC is 6.
Add 1 bonus for Helm of Balderan, now AC is 5.
Add 1 bonus for Ring of Protection +1, now AC is 4.
Add 7 bonus for Bracers of Defense 3, now AC is -3.

Now watch with Spell which sets Base AC to 6 and is cumulative with Dexterity.

Base is 10
Add 4 for Dex, now 6.
Add 1 bonus for Helm of Balderan, now 5
Add 1 for ring, now 4.
Cast spell (mage, level 1 armour), now AC is 0.
Add ? for bonus from Bracers of Defense 3? cus AC went to -3, not -7.

It was cumulative with the helm and ring but not with the bracers?

Seems that a 4 bonus in Armor is sufficient reason to cast the spell,
until you have the bracers, then nada.

Anyone know why?

If you look carefully, those set your BASE AC to 3, not provide a -7 AC bonus. The bracers set your base to 3, the armor sets it to 6. So don't bother with Armor if you have bracers of defence AC6 or lower, as it will do nothing

EDIT] minor corrections

[ 10-16-2002, 04:32 AM: Message edited by: White Lancer ]