Thanks for the bug report! We'll need some more diagnostic information in order to get to the bottom of this. Could you try the following:
- Close any other instances of RStudio open on your machine,
- Launch a new instance of RStudio,
- Get RStudio into the state where it's using 100% of your CPU.
Then, you can open a terminal (e.g. Ctrl + Space, type Terminal.app, and open that), then execute:
sample rsession > rsession-sample.txt
Then, you can send the generated rsession-sample.txt file over to us for analysis (e.g. share a link to that file in DropBox, or perhaps upload it to https://gist.github.com)