Are these RAW photos? If so, read this: Why does the color and or tone of my image change after import?
In other words, this is a normal thing to happen to RAW photos when you import into Lightroom and you can't stop it. You can create develop presets to be applied at Import to create photos more to your liking.
Are you importing JPGs or RAW images? Is your camera set to a specific 'scene' mode?
Have you tried turning off the Graphics Processor option in Preferences/Performance?
Also be sure that "Apply auto tone adjustments" is off in Preferences/Presets
First make sure auto tone is off as wobertc mentions. That is the biggest cause of problems. Second, if you have a Nikon, Canon, or Sony camera, the simplest way to stop this from happening is to set the default camera profile to "camera default". This is done by taking an image that hasn't been edited and going into Develop. Then in the camera calibration part you select "camera default" as the camera profile. The hold the alt/option key and you'll see the reset button change into "default". Click it and and select "update to current settings". This will now have the camera matching profile that mimics default settings on your camera selected as the default for new images. Again. This only works with one of the main brand cameras but does help with some of this confusion.