If you're still using Joomla 1.6, that's the first issue. You need to upgrade to Joomla 2.5. There's so many bugs and security issues with Joomla 1.6, it's not even worth investigating anything else.
Beyond that, are you using any of our extensions, or is this a general Joomla question? If it's a general question, it's best asked on the
Joomla Forums
. I've never heard of that issue, and wouldn't know where to begin with helping solve it (beyond upgrading).
Best of luck,
Alex
Joomla site offline does not work for joomla 1.6
