New problem on 2yr old camera - pictures too dark- can only adjust in manual or tv - any ideas?

Reset the camera. Then use your preset program modes. Your white balance is also probably off and you can adjust that in the menu settings. You can also try "bracketing" in aperture priority mode where you shoot at -1, 0, +1 on the aperture, then you can choose the best and there's an auto bracketing feature you can use for it. Really cool..

Also, remember that there's a large difference between what you see on the LCD and what you see on the TV and then printed on the page. This is largely due to being reflective vs. projective styles. So you it's not surprising it looks dark on the screen.

I tried resetting the camera already - it made no difference - I'm not sure if there is a further reset button. I also tried an experiment in manual following a suggestion - taking a photo of something dark against a light background in Manual then gradually increasing the fstops from 2.5 to 8. On the camera monitor as I take the shot, it shows that the image becomes increasingly darker but when I look at the captured images the difference is not apparent. The image darkness I am referring to is both on the lcd and my laptop monitor ... it seems that the ISO is stuck on one setting. I made sure that batteries used were newly charged and in good condition.