Hello, we have the same problem here. It not only occurs with ant files but also with many other text files, which should normally appear with the default “Courier New” font. Hard to say how to reproduce this behaviour since I have that problem since installation of MyEclipse 6.0 (we currently have latest 6.0.1).
Can you please check this out? It’s quite annoying and for now I am using an external text editor for editing simple text files.