I do see other people having this problem but I honestly can't tell you what the fix if any there is for it.
I would take it your using Windows?
Your CPU and GPU I would think should be able to transcode. Latest nvidia driver installed?

Are you allowing direct play on your devices.

I guess start ...

What are the specs of your computer and what are you trying to watch it on. Sounds like the PC you are trying to use as the server just doesn't have enough to transcode the video to the device you are trying to watch it on.

Congrats!