Most likely you got a new and defective monitor profile through Windows Update - but it's hard to tell without seeing. Can you post a side by side screenshot? Lightroom Develop > Edit in Photoshop.
In any case, don't change any color settings in PS or Lr. If you have, change it back. That's not where the problem is (but changing some of them could be).
I don't see this as very oversaturated in PS - but the skin tones are slightly more yellow, and the overall contrast a little lower.
I'd still say this points to the monitor profile. Are you using a calibrator? If so, run it again. Make sure it's set to produce version 2, matrix-based profiles - not version 4 and/or table-based.
Lightroom Develop converts from linear ProPhoto into your monitor profile, which is a more complex conversion than from a standard working space profile. That's why a difference is usually an indication of a profile problem.
Do you see the same difference between Lr Develop vs Library?
I tried to run the calibrator again. Spyder 3. No changes. There is no difference in between Lr Develop vs Library. What's weird, is that edited a full session the night before, and everything was fine. It just happened overnight. I was thinking one of my kids did something, but after checking all the settings, it seems everything should be great. I did download Portraiture 3... Would that have anything to do with the change?
...mmmmaybe...don't really know, but plugins can sometimes cause weird issues. Try to disable it.
Anyway, to test the monitor profile, try to replace it with a known good one - sRGB IEC61966-2.1 if this is an older iMac with a standard gamut display. It won't be entirely accurate, but the point here is to see if there is still a difference.
If it's a new iMac with DCI-P3 (wide gamut) display, there's really no generic profile that matches it, but Adobe RGB should be good enough for a test. You should also have a "Display P3" profile that came with the unit.
In the latter case (DCI-P3 panel), the Spyder3 isn't really quite up to it anyway. It was never very reliable with LED or wide gamut in the first place. 4 and 5 perform much better.
Remember to relaunch PS and Lr after a profile change. They need to load the new profile at application startup.