I have been thinking that a character and his equipment are separate target unless otherwise noted. So, when targeting a creature, only spells cast on that creature is cancelled, not the spells on the items he carry. So targeted dispel do not affect Magic Vestment of Greater Magic weapon.
Also, I have been thinking that an area dispel may dispel all the spells cast on his armor, shield, and weapon at once.
Say, a fighter is boosted by Haste and Bless, and his armor and shield are boosted by Magic Vestment, and his sword is boosted by Greater Magic Weapon.
*Targeted Dispel (the target is the fighter)
Make dispel checks for Haste and Bless (Only). If the mage is lucky, both of those spells may be dispelled.
Magic Vestment spells and Greater Magic Weapon are never dispelled.
*Area Dispel (the fighter is within the area)
For the fighter, up to one spells on him (Haste of Bless in this case) may be dispelled.
Also, make dispel checks for Magic Vestment spells (one for armor, one for shield) and for Greater Magic Weapon. If the mage is lucky, all the three spells may be dispelled.
That is how I have been played. But frankly speaking, I am not sure if it is definitely the correct way.