I too have that issue and have not put time into it.
When I was beta testing v8, I needed it to coexist with my production v7 system -- which, had been moved to a different location.
I wasn't able to get the web preview to work - I'm sure there was already a question about this and Vlad specified what needed to be changed in a config file.
If you get THIS before a solution from someone, I'd re-read any recent posts about v8 to find his answer.