Originally Posted by ThurstonX
I think the "video hook" driver that VNC clients offer for use might be the cause. I use TightVNC and purposefully disable the Video Hook option. Things aren't as smooth, but it's quite usable (esp. with ZRLE and 256 colors), and it doesn't mess with WMC either. Just something to consider if the problem resurfaces. I think the Video Hook is only active when you've VNC's into the server.
In passing I mention that I have RealVNC Personal Edition v5.0.5 installed on my Ceton/HTPC, very much for the reason that the PC is up 24/7 and when I'm out of town I want to be able to check to be sure the machine is still alive and well and recording as planned, and so that I can manually set recordings for one-off programs I didn't know about before I left town.
The optimal way to run video is with "mirror driver" enabled on the server (i.e. HTPC), for best performance getting desktop changes back from server to connected clients (i.e. my laptop on the road). I've run that way forever on EVERY customer "server" machine I've ever installed RealVNC on in order to provide remote support, and run that way right now on this Ceton HTPC as well.
Absolutely no problem with DCA "approving" my setup when I first installed Win7 Pro x64 on this machine and ran through the initial setup for WMC. The machine includes an external ATI HD5870 video card (no onboard Intel graphics), ASUS P8Z77-V Pro mobo, Intel i5-3350p CPU (no graphics). Dual 24" 1920x1200 Eizo monitors both connected with DVI cables to the dual-DVI HD5870. This machine was built back in December, and has a 4-tuner Ceton card in it for TWC/LA (including a Tuning Adapter for a handful of channels) along with a 2-tuner Hauppauge PVR-2250 for OTA/ATSC which I use for all local broadcast networks (rather than TWC, which re-compresses everything including OTA networks).
Have you run Windows Experience Index? That's required in order to be able to run DCA. It shouldn't have anything to do with RealVNC installed in my opinion.