First of all, US action not informing OBL operation, only reflect their concern about ISI commitment to war on terror.
There was not allegation that he was sheltered by ISI.
By the way spycraft itself business of deception, all spy agencies deceive each other to achieve their goals, it is same of ISI, RAW oe CIA.
Again there is no conclusive evidence provided that ISI is involve in recent events, just by a some US general say so does not amount to conclusive evidence.
In any case Pakistan army and ISI has to maintain delicate ballance between our interests and US interests, this all allegation started not because of their complicity with enemy but due to Pakistan Army's refusal to extend operation to south waziristan.
By the way Pakistan Army has lost more then 3000 Jawans and officers including a Lt. General, ISI which is a branch of Pakistan Army, and it is not possible for them to support same people involve in killing it's own people.
There are 3 categories:-
1) Alqaida
2) Pakistani Taliban
3) Taliban or other resistance groups in Afghanistan.
Pakistan army or ISI, fully committed with war with AlQaida and Pakistani Taliban, but apparently they did not move against 3rd, (there is no active support though).
Due to ongoing operations against Taliban there is huge problem of displaced people, opening new front would mean more people's displaced and army does nor have resources to provide them for full duration of operation.
Pakistan army already deployed more then 200K troops, opening new front means moving troops from borders with india thus weakening our defenses. Which army is unwilling to compromise.
In any case whether US or Indian like it or not the writing is already on the wall, true to it's history US already planning to cut and lose, and everyone else has to look at plan B TI prepare for what happen then.
It is in the best interest of Pakistan not to burn the bridges with whichever force likely to take over beyond repair.