Audio trouble

im having audio trouble i hooked up my sony bdps580 via hdmi to my sony strdh820 and hdmi to my epson 8350. everything was working great till all of a sudden in the middle of a movie i lost audio. i tried to reset everything unplugged. even got a new bdps590 but same problem no audio i finally unhooked the hdmi ofcourse losing video aswell then only hooked up digital coaxial. well i have sound but ofcourse no picture being that the hdmi is disconnected. as soon as i hooked up the hdmi i lost the audio but i have great picture. my question is can i hook up digital coax and hdmi but just use coax for audio and use hdmi only for video?? can i turn off the audio out on hdmi and turn on the audio in coax in the menu? how else can i fix this problem?