Graph text is "blurry" on X11 device

The problem I have is that after upgrading on Mac to OS X Yosemite, my graphs in R are blurry. In particular, the text and the axis that I additionally added to the graphics are blurry. Also I cannot access the history of the charts.

Do you know what could be the reason?

_{(source: bplaced.net )}

With this code:

X11()
boxplot(count ~ spray, data = InsectSprays, col = "lightgray", main="plot title")

      

        
        
        
      

    

the Plot Title and the axis are still blurry.