[SixOfSpades]

Since Mage Robes technically count as armor, then yes, you can wear armor while you cast spells. But if you meant that kickass Shadow Armor that you love so much, then no--although you CAN still cast spells from scrolls while wearing armor.

Wearing armor that is forbidden by one of your character's classes will block the skills of that class: Wearing armor that a pureclass Mage cannot wear will block the casting of any Wizard spells (Priest spells can still be cast), and wearing armor forbidden to a pureclass Thief will prevent you from Picking Locks, Picking Pockets, or going into Stealth. (You can still Detect Traps while wearing heavy armor, but you'll need to remove it if you want to Disarm them.)

Using Helmets, Shields, or heavy weapons will have no negative effect on the skills of your "weaker" class.

I *really* hate the spacebar on this keyboard.