Hi Paulo,
I went back in my emails when I had originally come across the superuser password change issue, and I actually just remembered a fix for this was issued for Jasper 6.2!! Please open a CA Support case, and request for fix T6D3123 to be provided. When you apply the fix it will deliver some files to the NX_ROOT\CABI folder, which you need to follow the post steps in the patch readme file which tell you to copy those files to the jasper server and then add some server attributes etc.
This should get you going
Thanks,
Jon I.