Are my installations/registry settings confusing my 5.1 setup?

[takearushfan]

Yep... me again,
In other threads I mentioned how my 5.1 setup was only playing in Stereo. However, a couple days ago I fixed it... all 6 channels playing exactly as they should. Unfortunately, I was experimenting with so many things in so many ways that I can't pinpoint what it is that fixed it. Yesterday, it reverted again Now, it's back to nothing but Stereo and I have no clue what I did to make it that way
If it helps you to help me, I should mention that I'm running Windows 7. I have AC3Filter installed and properly configured. I uninstalled and reinstalled my sound card... didn't help. I uninstalled and reinstalled Soft Encode... didn't help.
When I do fix this again, I'll be sure to backup my registry!
I was in the middle of a project, which was working fine. Then, for some unknown reason, it got screwed up again. I'm eager to resume my work, but, of course, I can't.
Please help
Thanks (again) in advance,
Justin

EDIT - What does work is to use Audition's Surround encoder and export a single 6-channel interleaved Wave. If I then use VirtualDubMod and use that Wave, it'll play back just fine... in VirtualDub. I haven't checked how it plays back in anything else. I tried using eac3to to convert the Wave to AC-3, but the AC-3 ends up playing back incorrectly as well.