Vista 64 prem. optical out sound stops, Any ideas?

Here is a run down. I build HTPC systems and when building these with Vista Prem. 64bit the sound may just stop working. The only way I have found to reactivate the sound is by going into the General setting of Media Center and restting up the Toslink. And "POOF" all is working fine again. There seems to be no general cause or time after booting. Now I do know that most of these system may stay on for many days at a time, yet some do not. The drivers are up to date and codecs are the same as you all list here. Don't get me wrong. The work around works fast and is simple but it is a pain for myself and the other owners. I am including the general components below.
Asus M3A78-EM - mother
Vista Home Premium 64bit
Phenom 9650 up to 9000's ( all quads from 95-140watt)
4-8 Gig ocz, Topram or Kingston Pc6400 Ram (always Matched)
All w/ seagate sata harddrives 500g-2t
All have LG Blu-ray or standard DVD drives
And also 450-600 watt PSU
After that:
some use the HDMI on board or have optional video card and TV tuners but ALL use Realtek (board) 5.1 or 7.1 optical sound out.
The hardest I have EVER made one of these systems work is All "quad" running 85% or higher longer than 10 secs and using 5.8 gig ram. ( just a working test I do on them) A side note though.. I do have to say it is "COOL" to see that much power being used on a simple system (whoo)

So I have looked through your forum and unless I missed something I can't find it... Any help?
-S
P.S. this is my first post so I must say - I will not sell to anyone in this fourm so please do not ask. I do not believe this is the place for that for me. I will only help with ideas.