Change/Translate Text (i.e. Modal Window)

Hi! I have a quick question: when someone click on the vote button without first choose a poll answer, a tiny modal window appears saying: ‘Please choose a valid poll answer.’

Is it possible to change the text with something else or to translate it in another language, without editing the plugin file? Note that I encountered the same problem using WP-Ratings (‘You Had Already Rated This Post. Post ID #12465.’), in case they work the same way ??

Thanks for your help!