What exactly do you mean by "preview window"? Library? Develop?
Do you get this cast in both Library and Develop?
Please post a screenshot showing the problem.
Right off it sounds very much like a broken display profile. Your photo viewer is probably not color managed and so doesn't use the display profile at all.
But yes, a screenshot would make things much clearer.
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Yes, definitely a defective monitor profile - the magenta cast in the gray areas of the histogram confirms it.
The bad profile was probably installed with a Windows update.
Since the Photo viewer doesn't use the monitor profile, it's unaffected.
As a (temporary) fix, set the monitor profile to sRGB (Adobe RGB if you have a wide gamut monitor).
You should then ideally calibrate the monitor with a hardware calibrator, which will create a profile that accurately describes your monitor.
Press the Windows key+R, type colorcpl in the box, and hit Enter.
Add the sRGB profile, then set it as Default profile. See screenshot (from Windows 7) below.
Yesssss! Thank you very much!