I have also encountered this problem (though only parts of my content disappears not the whole thing), and have reproduced the problem on two different servers, neither having the above mentioned plug-in; so I don’t think it is a plug-in compatibility issue. Seems this is some type of bug between the program and the TinyMCE editor.
I created a new page and posted a mid-sized (validated) html table into the editor. It views perfect, and i can publish it, and it looks fine. However, when i go back to edit it, half of the content disappears and the editor seems to have lost the data in transit between itself and the database. The same thing happens only more quickly if you hit Save rather than Publish. After the save and going back into the editor the data is lost.
I’m going to try the above mentioned fix: disabling the WYSIWYG options in my user profile as the only plug-ins i have active are Search-Everything and Search Hilight.