Stuck with "Staff of starlight"

[srx648]

After several tries, ( including change the order of activating altars ( and fight with gurads)), the shield just don't disappear

I think I'll travel to another land first and come back later to see if it will be solved...

[Belgarath]

Did you talk to all three mages maintaining the shield before trying to activate the altars?

[srx648]

yes,
I can activate the altars after talking with three mages, and Ordo is the patientest mage willing talk with me .

one thing strange is the texture of altar of chaos seems broken.
doesn't looks like others.