1080p mkv playback stutters

Hey guys, I have my HTPC hooked up VIA HDMI to my 65" LCD HDTV. When I set the resolution of the computer to 1920x1080 with progressive scan on at 24hz I get a little jutter while watching 1080p files encoded in an MKV container. It's not like the movie is lagging, but just kind of stutters a little every 1.5 to 2 seconds. The place where I notice it the most is in the opening sequence of like a starwars movie where it scrolls up the yellow text. You can see the text briefly pause for less then half a second and then continue. The problem also doesn't let the audio get out of sync or anything, like it will pause and then speed up to compensate or something.

When I watch 1080p movies with an output setting of 1080i, this doesn't occur. This only happens with a 1080p setting and it does it no matter what file I use.

I'm almost sure that it's some kind of driver issue somewhere that has to do with refresh rates.

Here are the specs of what I'm dealing with.

Computer - Intel Quad Core Q9600, 2gigs DDR2 800, 200gig sata drive, motherboard has 680i chipset with onboard geforce 7100 and HDMI out.

I am using the latest nvidia drivers (178.13) and the latest ffdshow and haali media splitter to decode the mkv files.

My HDTV is the Olevia 265TFHD 1080P LCD and it is connected via a standard HDMI cable.

I tried messing around with powerstrip (the program) a little with the custom refresh rates, but didn't really see any difference. And now I accidentally set it to a mode that can't be displayed on my tv and all I get now is a black screen.

Does anyone have any ideas as to why I'm experiencing this jumpy problem? Thanks.

The weird thing is that the problem is so consistant. It's like every 2 seconds.

I ended up reformatting my computer because of the powerstrip issue. But that gave me a chance to get the newest version of everything fully updated. The problem is still happening. I can't set my screen refresh to 60 while it's in 1080p mode. I can only go up to 30. I am using windows media player 11. This doesn't just happen with star wars though, it happens with any 1080p movie that I try to play. It's just really noticable in parts like the opening yellow star wars background story, or in a scene where a landscape is zooming in. you can look at any edges and see the momentary freezing.

While in 1920x1080 I can't set my display to anything above 30hz (interlaced).

I'm using vista ultimate 32bit. What can I use to find out the frame rate of the movie?

Where did you change this in ffdshow?

I am playing the files over a gigabit network. they play fine when I am viewing them in an interlaced mode, but when I switch to progressive scan, they do the stuttering.