Say a paranoid magic user has Blurring bracers of armor, Mirror Image, Blink, Invisibility, Wings of Cover, and Etherealness going. How to calculate the miss chances versus a normal attack, magic attack, force attack, and so forth?
Don't stack miss chances; instead use the highest miss chance that affects an incoming effect
The Rules Compendium says, "If a creature receives miss chances from multiple sources, such as from being incorporeal and having concealment, only the highest miss chance applies" (32).
Suspicious of the Rules Compendium?
The Rules Compendium—by here expanding yet not contradicting the core rules—, in this case serves its function as the Player's Handbook concerns itself with miss chances due exclusively to concealment (e.g. "Multiple concealment conditions (such as a defender in a fog and under the effect of a blur spell) do not stack" (PH 152)).