I wanted to try out the cool new R<-->D3 feature as announced here so i got todays daily build but ran into problems - cannot open old projects anymore (cannot connect to 127.0.0.1 rstudio crashes).
I know that the daily builds are unstable and should be used with caution - I just wanted to report this somewhere.
Switching back to the preview version and everything is back to normal.
I'm on ubuntu 17.10