After a recent Ubuntu update I didn't see the main menu bar of the RubyMine IDE (File | Edit | View | ...
) anymore.
This could be solved by changing a RubyMine registry entry:
ctrl + alt + n
> click on Actions
> type registry
> click on Registry...
linux.native.menu
and disable the checkboxAfter rebooting RubyMine, you'll have gotten the menu bar back.