not every selected letter is being extruded

 From:  pierrehansen
8631.1 
Hello,
I'm having difficulties to extrude the letters of the word "Binaural" in the attached file. Even if all letters are selected only "B, i, u ,r ,l" are being extruded. Very strange. Can somebody out there reproduce this phenomen and has an explanation for this behaviour? Very strange.

Thank you very much.
Best regards,
Pierre