I specifically remember, that I checked the spell resistance before and after clicking USE and it was 7 both times (did not change). So either the bonus is applied even for having the item in inventory, or there is some other, conditional bug.
What I am sure of is that when using the item, the Spell resistance value did not change.
The bonus will show if you select the item in your inventory, in this case the game is trying to help you do the math. if not and you are actually facing a real bug, as I said, bring on a savegame or atleast a screenshot, I am sure the dev team finds no problem using the tablet of spell resistance as I did not (Imagine I am trying to be friendly, but am in pain right now).
I was not trying to be mean or say you were lying, but merely saying that the tablet worked for me, which in turn means it might be a specific tablet, or a specific hero causing the problems, so additional information about the hero trying to use the tablet, or which scenario/map you found the tablet in would help root out stuff (its nice to know if it atleast was in a random map, that would rule out scenario's, and premade maps).
Next time it happens, I recommend saving the game the turn after you notice it, fetch the savegame from "Documents/My Games/FallenEnchantress/Saves" and include it on the forum using "www.dropbox.com", if your in a really joyful mood you can include the "Debug.err" found in "Documents/My Games/FallenEnchantress".
Thanks for your time anyway, not trying to undermine your bug report 
Sincerely
~ Kongdej
