Button Label text problem

[Redmond M.]

http://tinypic.com/view.php?pic=347e107&s=6

My calculator project button label text often looks distorted.  Please refer to the above screenshot, the bottom 3 buttons - which are the operations buttons sin, cos and sqrt.  The text looks like it's being cut off.  These buttons are 68x43.  I tried resizing the buttons but this did not seem to work.

I noticed that sometimes the text looks fine, but most often it looks distorted as in the screenshot above.  Anyone know the reason for this?

Thanks