this is crazy.. but i think the windows "security" settings of a folder [right click folder > properties > security] are the trouble makers here!

And as i said before, this is crazy .. coz i haven't changed/altered any settings to my download folder before.
On a hunch of logic i went to check it up when jdownloader kept saying "no permission" "No permission"! And there it was..

All's well for now..
Check back in after a while and let you'll know if it stays this way.