All browsers are pointing in the first instance towards the xml file as being undefined or empty, so the first step (unless we spot and fix an obvious error in the xml file right away) might be to replace the custom files by opening and editing the instances again, perhaps choosing a new configuration preset from the HTMLEditot UI (i.e. Advanced Manager Enabled), accepting all the default settings for now, and see if that will rebuild/repair the core functionality.
I'm not sure what you mean by 'stripping-out' iRite, did you completely delete the iRite folder before applying the HTMLEditor?
If just re-applying HTMLEditor with a new preset still leaves you with problems, I would (if it were me) delete the HTMLEditor Folder and start from scratch, as this would probably be quicker and (and ultimately bring more peace of mind) than chasing down and testing each glitch. It's odd that Jason is seeing it working OK - there may be a clue there than I can't see - I have tried in FF, IE8 and Safari - all with the same results. (Safari: "This page contains the following errors: error on line 1 at column 1: Document is empty. Below is a rendering of the page up to the first error.")
The attached zipped (xml and .js) files seem to work fine for me, maybe you could try swapping your existing files with these just to see if you can get beyond the first error messages (after backing up your existing ones). That may circumvent starting again or at least give us a clue or two. Maybe not, but perhaps worth trying anyway.
I believe the kfm tables are generated when you enable advanced file management and access the file manager online. Rerunning HTMLEditor from scratch (if you have deleted the tables) should recreate them on first demand (I think?). Jason will know more about that.
The WA Guys will know about the serial - were the two extensions both bought under the same account and are now on the same Downloads Page? It maybe that you could ask sales to move one copy to a new account to seperate them off if that is the case (sales(at)webassist(dot)com).
If nothing else, could you upload (zip, txt) your custom/xml file?