Prb accessing dimension from web administration

Hi Experts,

Does somebody face this issue :

I've 3 users with BPC Admin Right.

For One User, i can edit members of dimensions

For the others, while i click on link to edit members, nothing happens

Also Strange :

While I make a Back Up and restore, the problem seems to disappear.

But , it is not acceptable as solution.

Any Idea ?

Tks for any suggestion,

Olivia.