Hi
I had exactly the same problem and a few google searches led me here.

Since you mention you have a Panasonic Plasma (as do I) I did the following and it sorted me out.

To be honest I'm not sure exactly what sorted it out of this list but I suspect the TV config was the answer.

Anyway:

1. On the Panasonic TV - "Menu > Settings > Other Settings" Set Intelligent Frame Creation to OFF.
2. Use Shark 007 Codecs install standard then 64 Bit. Change the following Settings:

Settings Application 64 Bit

SWAP Tab > Disable Windows Media Foundation > Ticked
> Disable Windows DMO Video Codecs > Ticked
> Disable Microsoft Video Decoder > Ticked
MKV Tab > Playback > Use LAV Splitter > Selected

Setting Application (32 Bit)

SWAP Tab > Disable Windows Media Foundation > Ticked
> Disable Windows DMO Video Codecs > Ticked
> Disable Microsoft Video Decoder > Ticked

MKV Tab > Playback > Use LAV Splitter > Selected

3. Check the Video Card Refresh Rate. My Plasma has a Refresh Rate of 600HZ or something Mad. Windows seems to set this to 50HZ for some reason. Change this to 60HZ:

Control Panel > Display > Adjust Resolution > Advanced Settings > List All Modes > Choose 1920 by 1080, True Color (32Bit), 60Hertz

4. I also use my HTPC for gaming with an ATI R9 Series and also saw screen tearing sometimes in games. Usually the V-Sync setting in the game sorts this but I sorted this as well in Catalyst Control Center by:

Gaming > Application Settings > System Settings > Frame Rate Control
Wait for Vertical Refresh > Yes, unless application specifies
OpenGL Triple Buffering > On

If you don't game though or use an ATI card then forget this.

All of this sh*t p*ssed me off until I worked it out so I hope it helps others.

Good Luck!