Seems there are some minor install problems with the latest version of AdWords Editor.
There was one discussed on the forum here. And Google gave some information about what they had been seeing.
"The potential exists for v5 on Windows to crash on start-up. This will most likely be experienced by users who have Google Toolbar for Internet Explorer. The work-around for this is to remove all copies of Google AdWords Editor from the Add or Remove Programs Control Panel (there will probably be two), then reinstall," Google suggested.