CKEditor install not working with previous FCKeditor created nodes

Hi,
I'm hoping there is a simple explanation for what we've run into, but I'm sorry to say that it's really hard to determine a pattern for some of the screwy goings on. ...

Background: Two installations of Drupal 6 one with Newsflash theme and another with CTIFlex theme. FCKeditor has been used for a while in both installations. Upgraded to CKEditor, followed instructions to the letter and then switched over to CKEditor... Did NOT uninstall FCKeditor.

In create mode, CKEditor seems to work fine, though at first there seemed to be an issue regarding CSS because in them CSS we were unable to get the cursor to work in the box. But that seemed to clear up after we cleared cache on the server and on the browser and ran cron.

But in edit mode, that is editing pieces created in FCKeditor, it gets odd. Several "story" nodes reveal no content when in edit mode -- almost as if there is a white overlay over the "body" that is white rather than transparent (text does appear in plain text mode). That led us to think it was a CSS problem, but a) we tried all the CSS options and no change and we cleared cache after each one and b) this pattern was NOT replicated on all stories. Some stories we can edit just fine.

What's weirder is that the blog type seems fine in edit mode. So do wikis.

So we're hoping it's just a few files and we may copy them into new nodes and spike the old ones, but since one is a multi site configuration with much content, we hesitate to make the switch.

It seems there is a conflict here somewhere and it makes me think there may be some issues in the port from FCKeditor to CKeditor that result in inconsistent behaviors. Any ideas?

And does it have anything to do with the fact we did NOT uninstall FCKeditor?

Thanks much in advance.

geoff