Poor screen position, too small font, screen too bright/too dark, poor sitting posture are all commonly reported causes of chronic headache.
Recurrent headaches are a very frequent complaint among heavy computer users. Typically these are caused by a multitude of issues regarding computer use. If they occur the same time every day or if they do not appear on non-work days, these are the clues that point me to a computer cause (even though you are using a lcd tv which reduces the strain significantly).

Often when I tell my patients that I suspect it is their work environment, they come back and tell me me how they fixed it. Poor screen position, too small font, screen too bright/too dark, poor sitting posture are all commonly reported causes of chronic headache. When in doubt, I just tell them to trade offices for a couple of days. If they feel better in the other office, then it suggests that it is related to their personal work environment.

Poor eyesight is frequently believed to be a cause of chronic headaches although I believe that is very overrated. What I have seen a few times is that people with glasses having too strong of a prescription. Type-A people when getting refracted for glasses will mistakenly report that higher and higher powers make them see better. To check for this when you get your glasses, just ask your doctor if the manual refraction is close to the computer-predicted, automated refraction. If the manual is a lot higher, then over-power should be a consideration.

Back pain is a frequent complaint in my office as well. In the general patient population, chronic back pain is often a sign of depression; however, in the geek this is more frequently due to work conditions or to overuse. Poor posture, incorrectly sized chair, or poorly positioned monitors are common culprits.