Webatelier,
I've spent more time on your site than any others lately.
Right now, things seem to be working. I really didn't change much. I re-ordered the JFBCSystem plugin, and was trying to diagnose the cause of another odd thing I was investigating in IE. However, things just started working then. I can login and logout repeatedly from the site with or without www. Not sure what changed, and it may be intermittent. We'll test again, and we definitely suggest you test a bit too.
The biggest issue I was seeing was that if I would try to go to the following URL:
www.davidvandyck.be/index.php?option=com...bookUser&return=Lw==
In IE, the URL would automatically switch to:
www.davidvandyck.be/
That URL above is for logging the user in, and if it can't be reached, that would explain the problem. I was seeing that with the logout URL too. Basically, to test, I was editing the 'index.php' file in the main directory, and putting a "exit;" at the very top. When I'd navigate to the URL above, the page would be white (expected, Joomla wasn't executing), but somewhat was changing the URL back to the homepage. If I went to other addresses, like:
www.davidvandyck.be/index.php?option=com...t&view=article&id=12
The URL would 'stick' properly, and not revert to the homepage.
I tried to look at your .htaccess file to see if there was anything in there that could be causing a redirection, but I couldn't get into it. I installed a different file manager (OSE FileMan) as well, just so you know.
Hope the above explains what I did.. and if you have any ideas why certain URLs would just redirect somewhere else before Joomla actually executes, please let us know.
Thanks,
Alex