I'll run through the process from the top, just in case anything catches your eye...

Before we start, I'll point out that if you are using component video, it can be assigned to any video input, so there is still the possibility that the analog audio is going someplace different.

First, verify that the stereo analog cables are connected to Video2 on the rear panel (that's near the very center of this huge picture , just to the left of "Video 2 In"). Also confirm which component input you have connected the Wii to (it sounds like you're successfully using "Vid2", the left-most component input, located at the top left corner of the rear panel).

Once that's done and all is in order, go to the 990's setup menu. In the "INPUT CONFIG" screen, the Video2 input is the third choice from the top. The name can be edited, in which case the third choice in this menu will show that revised name instead of Video2. Go to that choice and press SELECT to enter that sub-menu. Once you are there, the AUDIO setting should be ANALOG (which tells it you use the analog input associated with Video2 - the only analog connection that this input can use). The VIDEO setting should be COMPONENT2. (Note that you can also select COMPONENT1 and COMPONENT-DVD here, as the three component inputs are not locked into a single input.)