Help! I can't seem to insert a Toslingk cable into any of the optical jacks on the 990, or the one on my LG LST-3410A. The plug soes not go in far enough to lock in place, and I dont want to force it. I have the long flat of the plag adjacent to the long side of the jack. Am I doing something wrong, or is Toslink not the right connector for these optical jacks?