No matter the type of datasource, even if the table has only Static Texts it's not being rendered in the Preview. The report was compiled with success. There is data being read in the "Report query" windows (when option "Edit query" is selected and an ArrayList is loaded).
Also, when I open the JRXML file again, the table disappear.
It only works when I save the XML code on Notepad, then open it again in iReport.
The issue was the compatibility, set to JasperReports3.5.1. Changed it to Last version and it worked.