Downloaded apps do not start, error -10658
This seems to be a problem with permissions in the bundle itself. Usually the execution flag doesn't get carried over from the DMG image.

Try, for the sake of curiosity to set the execution flag like this:

chmod +x /Applications/RubyMine.app/Contents/MacOS/&lt;name of the app&gt;


Note: replace &lt;name of the app> with the name of the app (it will probably be "rubymine", but I don't have that app to confirm the exact name of the binary. 

If you're in doubt, right click on RubyMine.app, do a "Show Package Contents" and navigate to Contents/MacOS/ folder and see what's in there. Perform the above command (chmod +x) on that file and try again.

I think it should be: 

chmod +x /Applications/RubyMine.app/Contents/MacOS/rubymine


update: I've downloaded RubyMine and the above command will work, however, for what is worth, I've got to say that mine had the execution flag so I didn't have any problem with it. Have you checked?