Problem when add administrator for Analysis Server ( SQL Server 2008 R2 )

Question

I'm trying to add a user as an administrator in Analysis Server, doing this:

1 - Connect - Analysis Server - Right click on the Instance - Properties - Security - ADD :

This number was already there, So when I click ADD and insert the user to be administrator, I see this error:

It says in English:

an error occurred in the system ( microsoft.AnalysisServices)

But what error? I can't add anyone. I can't even add myself ( I'm AD user of all servers ). Can't even add, too, the account I use to start services ( It has domain admin full privileges ).

Obs: This is our test server. We need to create analysis services objects via software. I'm trying to add the software user as administrator here to be able to create a cube.

EDIT1:

Trying to trace the error, I only get this:

The same useless information.

Answer 1

After days with this problem, I deleted that number, and could add users with no problem.