In 1.5.7 a new feature that filtered the source/HTML of articles had been added. It was a new parameter that was no in the global article parameters.
When it had been added, it didn’t have any options set as default. This actually caused a minor weeing contest between some ex and current devs. I had noticed the debate, but didn’t think too much of it.
Now, a few weeks later, what had been happening was that I had been editing my articles with the embedded flash objects in them, but had never set any default values for the filter. So, they were getting stripped out, even when I had the WYSIWYG editor turned off.
I realized my mistake and hurriedly set some default values for the new content HTML filter.
Morale of the story? Maybe sometimes its better to keep one step behind the release cycle and THOROUGHLY read the change log.
Or, you could just use a managed Joomla hosting service like Simplweb where we do that for you!