Hypersmurf
Moderatarrrrh...
The item isn't suppressed. It still works as normal. However, the _effect_ that it grants its user is dispelled (but can be reactivated).
The slippers aren't an activated item, though. Simply by being worn, they enable movement on vertical surfaces. Any time they aren't being suppressed, they work.
Bracers of Armor? Gloves of Dexterity? Mantle of Spell Resistance? Would you have all of these stop functioning until the user's next action, which he must use to reactivate them?
In the case of the ring of invisibility, the user "becomes invisible, as the spell". That sounds a lot like an ongoing magical effect, even if the source of that effect was an item. Much the same goes for the flaming sword. There's nothing stopping the user from going invisible again on the next round, or reigniting the sword.
I'm more willing to consider these ones, because they are activation-required items. Unlike the slippers.
But I'm still doubtful
-Hyp.