I don't see a link to the manual but many of those optical to analog convertors are LIMITED in what optical audio will be converted. Most will not work if the output is 5.1. Look around for any other output options.

http://www.hdtvtest.co.uk/news/samsung-le32c450-le26c450-20101001847.htm and other places show a HEADPHONE jack which should be fine as it's analog and stereo.