I have done that already several times after each install. I am now not getting any error, but its still not loading the preview. This is really hindering my ability to actually work.

actually no error banner appears, if you read what i said in my message, it just spins and spins "Preparing iphone Simulator for Previews" its been doing that for about 14 hours. for a Powerful Macbook, this is kind of stupid and clearly a software error.

I have done feedback with Diagnostics and have no reply. this is really stopping my workflow

I tried what you said... still did not work. This is a fresh install of an OS and of Xcode on a brand new computer, this is crazy. I have submitted feedback earlier this week and no one has responded. I think i want me $3800 back..