Vista - Analog 5.1 in Vista x64 ultimate

I have an older set of 5.1 analog Logitech x-530 speakers. OS is Vista Ultimate x64, with a eVGA 680i LT SLI motherboard (122-CK-NF63). I'm using the onboard MB 6 channel sound.

Here is what happened - I noticed that I did not have my center channel/sub (orange 3.5mm plug) plugged in correctly, so I plugged it in (Front - green & Rear- black; speakers all already worked fine) and tested the center/sub.....nothing. No sound from either the center channel or the Sub, but still sound from all the front & rear speakers.

I searched & downloaded eVGA audio drivers for the 680i (not sure where my original MB disc is, but I know those drivers are older), dated 9/2008. I install the drivers and it installs Realtek HD audio software. I test again and sure enough, the center channel and sub now work....BUT.....now the REAR channels do NOT (front speakers still work fine).

When I unplug the black rear channel jack & plug it back into the MB , the Realtech HD manager does not detect it (the black plug in the picture remains greyed out).

Ideas? What am I missing here.