Perhaps your situation is different. I assumed it as a problem on the server, so I submitted a service request to them and listed the pages that I could update the content on. They tried it and it worked, so I went to a different client system and it worked for me to. Then I started to adjust he IE settings and it all worked again. In my case, I was getting the error with all content editor web parts. However, I could edit the text in FrontPage, when the IE edit wouldn’t work.
In summary, I had a problem, the hosting company couldn’t repeat it and when I adjusted my IE settings, the problem went away.