I installed the FCK provider 1.0.0.9 BEFORE the upgrade of DotNetNuke.
There was an error because it turned out not all of the files were uploaded successfully. I uploaded again but still I couldn't edit except inline but that somehow changed some of the inline styles!!
Next thing I tried was to upgrade just the text editor (to 4.05), but as others I missed the fact it requires DNN 4.5.x. so I downgraded back to 3.03.
Then I did the upgrade to DNN 4.5.5.
Problem is while it doesn't apply changes to the settings it doesn't log errors as well :(
The only errors loged after the upgrade are prior the upgrade of the CATALook .netstore to match the DNN version and some strange smtp errors for the CATALook after the upgrade - strange because it says something like smtp is not set but when I check the store settings smtp is set.
And while editing text in rich text editor isn't working all the time, I can make changes to settings (module, portal, host) on irregular base.
I'm really puzzled.