Hello Tim Chamberlain,
You can find instructions on uninstalling the RadEditor for MOSS in the following help article http://www.telerik.com/help/aspnet-ajax/uninstalling-radeditor.html
. In your case you need to perform steps from 7 to 13.
There should be no problem using RadEditor for MOSS in 64 bit environment. What I suggest is trying to deploy the solution once more after successful uninstall.
the Telerik team