I saw your message ... I'll working on your test envirnoment this evening (I can't access it from here now).
Anyway I saw the jinc.log and I would like you try to execute those query against your database server
SELECT sendername, senderaddr, type, name, description, disclaimer, optin_subject, optin, welcome_subject, welcome, default_template, optinremove_subject, optinremove, on_subscription, jcontact_enabled, captcha, front_theme, front_max_msg, front_type, attribs, replyto_name, replyto_addr, notify, notice_id, input_style, suspended FROM #__jinc_newsletter n WHERE id = 1 AND published = 1
and
SELECT sendername, senderaddr, type, name, description, disclaimer, optin_subject, optin, welcome_subject, welcome, default_template, optinremove_subject, optinremove, on_subscription, jcontact_enabled, captcha, front_theme, front_max_msg, front_type, attribs, replyto_name, replyto_addr, notify, notice_id, input_style, suspended FROM #__jinc_newsletter n WHERE id = 6 AND published = 1
where #_ is your Joomla! table prefix. That query return just one row, but in your environment I guess is returning an error or an empty result.
Let me know.
Lhacky.