Today I noticed the following error in the event viewer "System.Exception: Error loading FCK setting (Reverse HTML Encode output) ---> System.FormatException: String was not recognized as a valid Boolean. at System.Boolean.Parse(String value) at DotNetNuke.HtmlEditor.FckHtmlEditorProvider.Fckeditor.LoadFCKCTLSettings(Boolean mAdmin) --- End of inner exception stack trace ---" with DotNetNuke 5.

This is how I work around this issue.  I search many forums and found the following articles that almost resolves the issue.

http://www.dotnetnuke.com/Community/Forums/tabid/795/forumid/127/threadid/123082/scope/posts/threadpage/2/Default.aspx
http://www.dotnetnuke.com/Community/Forums/tabid/795/forumid/127/threadid/282168/scope/posts/threadpage/3/Default.aspx

Also went to DotNetNuke Gemini and found an issue posted with no fix. The only close to a solution I could find was set "HTMLEncode Output" and "Reverse HTML encode output" to yes in custom editor options.