When using firefox on my site, I am unable to edit any content in the editor on certain pages.  This problem is inconsistent.  I have been able to reproduce the problem however on your own webpage at http://cutesoft.net/example/MinimalConfiguration.aspx

I have multiple pages that were working, but suddenly stopped.  We did implement a new default config file, but even after reverting it back to its default state it would still have the same problem.  Any ideas?  Thanks!