Hi Romuald,
sorry but it isn't clear for me where is the issue.
You have the CATEGORY.XLS file in Adminapp and if you open it directly with double click what happens, it opens?
With SSMS you see that the table dbo.mbrCATEGORY was renamed as
DOMAINAD\BPCSYSADMINUSER.mbrCATEGORY?
If so try to rename this table or recreate the old table with SSMS.
Kind regards
Roberto