This is a common problem with LCD TV's and even some plasma. There's a few threads around here about it. Obviously the people involved with making cable boxes or HDTV's (take your pick) don't care about this serious issue that's affecting countless thousands of people and are just ignoring it.
The fix, that worked for me (42RV535U with a Motorola DCH3200 box), was two layers of plain white paper taped over the IR sensor window on the cable box. For others what's worked has been 1 or more layers of scotch tape or masking tape, or sunglasses, and others. So in your case I would try the paper, 1 layer then 2, maybe 3. Just take a small piece of paper and fold it twice so it's the size of the IR sensor, then tape it but don't let the tape go over the sensor, just tape it on the edges (may or may not even matter).
What's happening is LCD panels (their backlights) are strangely giving off spurious IR noise that's interfering with the cable box's IR sensor. I don't understand how that's possible since the backlights (fluorescent) are in the UV range, opposite end of the EM spectrum from IR. The paper/tape/whatever acts as a filter for this IR noise. It won't block (much) of the IR band since it's a long wavelength compared to the short wavelength of UV.
Obviously the IR sensors in these affected cable boxes are also capable of receiving other problematic interference wavelengths. The manufacturers must start adding an additional component to the dark red color of the plastic over the front of their cable boxes.
