We have discovered that spyware or adware can cause some ActiveX control, such as the editor, to no longer function properly. One in particular that we have seen crash the editor are pop up blockers and the Alexa toolbar.
It is recommended that you scan your system for spyware. If you use the latest version of McAfee VirusScan, it should detect those files and remove them. You can download Spy Sweeper which gives you a free scan to remove spyware/adware.