Reporting Services Query designer toolbar disabled

Hi to all , i'm trying to modify an mdx generated by query designer in "Design" mode.
I would like to switch to query designer in "Query" mode but the query designer toolbar and its button "Change Type" appears to be disabled.
In this project i use a shared data source and the data source type is Analysis Services.
In another project I followed the first basic Tutorial on Reporting Service ("Sales Order" report) so data source it's SQL Server and query designer it is locked to Query Mode and i cannot change it to Design Mode.
Thanks for help.
Alberto De MarcoI'm not sure which buttons you are referring to. Could you attach a picture of what you are seeing?

-Albert