Display not fluid

I have a problem with my 2 display.
 
One is a regular 24" 1080p monitor plugged with DVI and the second is a Samsung 46" Smart Tv connected with HDMI.
 
Sonar is on the Tv which is the secondary screen and the mixer is on the 24" monitor which host the desktop.
 
When I play back my project the image blocks, just like when I press the "Pause/Break" key but a bit less dramatic.
 
If Sonar is stopped, with Aim Assist on, the aim assist dotted line does not run smooth either.
 
If I disable one display the problem seem to disapear.
 
My video card is a Firepro V4900 and my motherboard is AMD 990 chipset (FX-8350 cpu).
 
I thought it was the video card so I tried with an Nvidia gt240, same exact thing.
 
I don't know what's hapenning, I use 30% of my time working on music and 70% troubleshooting my &?$$# system.
 
I have 7 different crash dump files on my desktop for last week only, I wish there was a way to know what the hell is happening.
 
Well, thanks for any help, I'm tired.

Thanks lfm for your reply!
 
Actually I think I found what is plaguing my system.
 
Like I said I had a lot of crashes and never found the culprit. Today I finally disabled the only device I did not want to disable, the built-in Realtek Ethernet port.
 
I never disabled it cause I need it for my Nucleus to communicate with the computer.
 
Now that I have disabled it, the video card display a smooth image and my pcie Madixtreme achieve very nice latencies.
 
I have to try with with all my troublesome projects to be sure but so far this seem to make a real difference.
 
Edit: Well, it seem that disabling the energy saver and the 'green ethernet' thing in the advanced option of the ethernet adapter helped a bit. I re-enabled everything. Then I reinserted the mcu + extender plugins. The system became instable again. It look like the Nucleus cannot work in my setup...