Open src editor tab, put caret somewhere and try again (in your case probably was focused some component which context didn't contain info about name of current active project). Also check that "rake" gem is attached and SDK is set in RubyMine | File | Settings | Ruby SDK and Gems tab.
Please reload list of known tasks - "RubyMine | Tools | Reload Rake Tasks.." action.
That button is not clickable...i wonder why.
Open src editor tab, put caret somewhere and try again (in your case probably was focused some component which context didn't contain info about name of current active project). Also check that "rake" gem is attached and SDK is set in RubyMine | File | Settings | Ruby SDK and Gems tab.