I upgraded to OS X Mountain Lion from Lion over the weekend. Everything seemed to work fine, although was prompted to install new JRE first time I ran RubyMine (4.5.4) after upgrade.
Now, I am seeing that the code inspector appears to be hung -- the little icon in the upper left of the editor window shows the "eye" image, and reports "Performing Code Analysis" indefinitely. I have stopped and restarted RubyMine. The * in the bottom status bar reports no active background processes. If I introduce an error, nothing changes. I tried changing the settings of inspections. I tried going into Power Save mode (disables inspections) and then back.