Try adjusting the Film Mode option on the television to see if that helps with some of the judder you're experiencing. If you change the option on television for the input that the Blu-Ray player is connected to, it won't affect the other input that the cable box is connected to - the inputs are independent.
The only other option I can think of is to adjust the film mode option in the Blu-Ray player.
Recently I purchased an HP Blu-Ray player to connect to my Samsung LN32B360 LCD TV. While the picture quality is crisp and the audio is perfect, I find that when I watch DVDs they are subject to smearing and Blu-Rays appear jittery when being watched. I have the Blu-Ray set to 720p which is the max resolution for this TV to no avail.
I was wondering if this problem could be caused by the HDMI cable as I also have the TV connected to by HD Cable Box and have never experienced any problems with that HD content.