Set the power supplies for the cameras to the following:
A-5
A-6
A-7
A-8
Your transceiver (TM751) is set correctly, however, it should not match one of your camera codes.
Change your CR14A remote to operate the buttons as A-5 to A-8.
Make sure all the cameras and the receiver (VR42A) are set to Channel A. Also, you may want to try the other channels, which are B, C and D. These channels are not the same as house codes, hopefully this is not the confusion. The cameras have a small rubber cap that covers their channel setting switch on top of the base of the camera. Check the camera manual to find out which way the switch needs to be set for Channel A, which may be different than what they are currently set to.
One other thing, do you have the VR42A receiver plugged into the TM751 transceiver? I would not recommend this.
Also, do you ever hear the TM751 make a clicking sound when you turn any of the cameras on or off?
The other thing that could cause some cameras to work and others not to work is if they are plugged into a different phase of your house wiring. Most homes over 2000 feet, and many 2 story homes, actually have 2 phases of wiring split from the 220V coming in from the utility lines. Typically, without some type of a coupler, the X10 signals will not crossover to the other phase, which would not turn your cameras on that are on the opposite phase of your TM751.
Hope this helps. Let us know what you come up with.