The patch upgrade from IntelliJ IDEA 15 142.4675.3 to 4465.2 did not go well on OSX.
There were problems with three files, two of the third party readmes and the third a currency config file, I think. In all cases the problem was Access Denied.
After that IDEA would not start. because of an exception
So I had to do the full download and installover instead. I pretty sure the previous version was a full install over too.
Screen shots of the exception attached