Format text in validation data input box

Hi there,

I'm using Excel 2011 on Mac; I created a Table with several entries. On some columns I added Data Validation rules, with an "Input Message" attached, which appears in a box next to te the cell when I'm about to enter the data. Now, how can I format the text displayed in this "Input Message" box? It turned white, and I can't read it anymore.
Best regards,

Atride

I noticed that if i quit Excel and then open the file, the box has black characters, even though after a while it turns white again.