I am not sure about your update page but I have seen where a string replace command that is used when the field for update gets automatically populated by the database can create this problem... while it works great for text areas without rich-text editors, it seems to cause problems for special items in iRite such as images or the example you describe.
The easy fix is to go into the update page and where the iRite instance is, you'll see the variable for the iRite attributes such as location, height, width, etc. and then it will hold the value that the database currently has and will look like this (please note that this code from one of my site... so it will vary slightly on yours):
(str_replace('"', '"', $row_WADAblog['content']))
You need to get rid of the str_replace and just pull the value from the database, so your code should be amended to look like this:
Like I said, I'm not sure what your code looks like because the installation of PowerCMS does not have this code automatically on the update page but I know that the string replace method gets added when I add an iRite instance to a form created in DataAssist.