Maybe you should reset your BS5. When in Standby mode disconnect from the mains for a few minutes and reconnect. BS5/BM5 will automatically start up.
Set your BS5 to audiomaster:YES, A.OPT.1, BL5:YES. BL5 setting: L.OPT 0
Check the L/R switches on the back of your BL5s. When you change the spdif cable left - right, you have still no sound on the LEFT speaker?
Does it work properly via Powerlink?
Has your BS5 got the last update? If yes, try the CD/A.MEM setting instead of N.MUSIC, N.RADIO.
Your connected TV was a masterlinked Beovision?
Stefan