OK, I finally was able to get some time on this.
# If you use bash:
and then played the "h264info.com/serenity_hd_dvd-trailer.zip/Serenity - HD DVD Trailer.mp4" video. The vdpau playback problem (which is easily reproduceable) occurred again, and I posted the bash shell output when the error occured and the output of running nvidia-bug-report.sh as root as attachments to this post.
Reference the desktop corruption that also occurs, I note now that is specific to the desktop background, ... other openSUSE users have reported something similar in kde3 and kde4, and it may be associated with problems noted in this openSUSE thread:
In my case it does occur immediately if an openSUSE desktop theme is used (it takes minutes to occur with the classic KDE theme) and the background corruption also occurs quickly if large icons are used. ... whether that corruption problem also leads to the vdpau problem, I can't say.
Reference the 300 watt requirement for the 8400GS PCI card, I'm no expert in this. That requirement is straight off of the BFG GeForce 8400 GS PCI (512MB) specification sheet, where under minimum system requirements, they specifically state "300 W system power supply".
I do not have MS-Windows on this PC (an athlon-1100 with an MSI KT3 Ultra motherboard and 1GB RAM), so I can not test it under MS-Windows. However I may in the course of the next few weeks move the PCI card to another slightly newer PC (4 year old Asus A7N8X Deluxe with 2GB RAM) and I'll report on the results with that.