No worries. I reckon we'll be able to get you rolling in short order.
I'd expect that if you've tested MC then you were able to get audio playback happening at least once, so it's unlikely that you're dealing with something major.
First thought, "Is MC19.0.67 the latest stable version?"
From Standard View, check by navigating to Help > Update Channels > Stable (check)
Then check for updates (Ctrl+J) and let MC do its thing.
Second thought, "Have you checked the Wiki?" .. i.e. this page of useful help topics?
http://wiki.jriver.com/index.php/Category:Frequently_Asked_QuestionsFrom that page, you'll find this entry on Audio Setup:
http://wiki.jriver.com/index.php/Audio_SetupHave you worked through the noted steps and where do you strike problems? Normally the "if all else fails" option is to pick "Direct Sound" in Audio Output Mode. Have you tried this? What happens?
Also, can you tell us a little bit about your hardware? PC, soundcard, amp/speakers? If you've got some complex, HiFi audio rig with an oddball interface or proprietary audio driver, then that may indicate other avenues of investigation.
[EDIT: Oops - jmone beat me to it. Posted with some double up because it was already written. Some slightly different ideas that might help anyway.]