Hello Sir,
Our products are well tested on all common browsers including firefox. For satisfaction we have again cross checked. That does not happens as we do it on Firefox 3.5 and Windows Machine. Can you please tell me about the specific version of firefox and cuteEditor you are using, this may help us in solving your problem. Please try to install the latest stable version of firefox and check it again to make sure some kind of application or plugin is not interfering with your browser. Also try the SafeMode for firefox and see the response. I hope things will work fine in the SafeMode when all plugins are disabled.
Thank You, darknessends.