You don't need to go into the registry. You simply need to un-associate your files with CS5.5 using the normal File --> Organize --> File associations or Extras --> Folder Options --> File associations. And in addition you will have to make all those tools behave that add their own generic file handlers like virus scanners or packers. You're simply running out of context handlers, that's why you can't associate your files.
This actualy worked well. However, it did have an unintended consequence I now need to resolve.
Windows assigned a generic AE icon to my CS4 files now (you know the one I mean...with the white background). How do I get my AE icon back when opening these files?
Unforntatly not. He refers to the File --> Organize --> File associations or Extras --> Folder Options --> File associations. I personaly have never found anything like this but checked in Windwos 7 under "Defaults" and was able to associate the CS4 app there after some luckily finding it now present in the drop down menu.
However, there is no where I see that will allow me to browse and icon and assign it. If you are running Windows 7 and look under the Defaults menu in Control Panel you'll see what I mean.
There must be a way to do this somewhere I hope?