MPG3 Problem

[Cal D]

I opened up a wave file in CEP. I tried to do a SAVE AS in order to save it as a MPG3 (I have the plug in). When I did that, i got a message saying "No encoding format chosen: You must choose a format from the list" BUT..under the "available format" list, therer are none....so..how am i supposed to choose one?

Any help would be great