I’d leave 8 on your system at least for awhile until you sort this out. Different versions of Cubase are entirely separate installations and don’t really impact each other. I’d open the Project in C8 and poke around to see if GA is used on any Tracks.
Can’t recall if C8 had the Plug-in Manager yet, but if so that would be another place to look.
Importing Tracks into a new Project is likely the quickest way to recreate the Project. If importing Tracks also freezes the Program then import the Tracks one by one to find the culprit. Or if you have a huge number of Tracks it is faster to do half at a time and if one half freezes split that half into 2 quarters & repeat until you get down to one.