I have just purchased some Fostex PM04 monitors, and for some strange reason only one speaker is playing...

This happened last week at a friends house with his speakers and i assumed that he had a faulty one, but it turns out his speakers were ok when he hooked them up to his turntables. I know the outputs should work because they worked fine with a pair of Krk's the first time i got the s4.

Am i going wrong somewhere with the settings...?