When a document is already open in the R-GUI opening a new file using File -> Open Document, freezes R, producing the spinning wheel of death (which continues for at least 20 minutes). This has happened multiple times and only when using the R GUI.
This is a critical issue because there doesn't appear to be a workaround without force quitting R and losing data.
It may be critical (to you), but it is not very reproducible. There are several workarounds, so it's not critical in the bug repository sense.
There have been similar reports, so we're not doubting you, but it isn't immediately reproducible for be with 3.2.1 Patched (r68681), OS X 10.10.4.
You could try upgrading and see if it has disappeared in newer builds, but it could be more fruitful if you could catch it in the act and find out where R.app got stuck. That's a bit tricky to ser up on a MAC, I'm afraid,