Is what you see in Library the original, camera-embedded preview or is it just a messed up version of the LR-rendering? You can test this by making a significant change to an image with the problem (Exposure -4 or Saturation +100) and see if the Library Preview also darkens (or the colors saturate) significantly or not. You might also try explicitly telling LR to recompute the Standard then the 1:1 preview to see if either of those show up in Library.
If the Library view never shows any LR adjustments and is always the camera-embedded JPG preview or a LR-preview from some days ago that never changes no matter what you do in Develop, now, then your Previews cache is likely corrupted and the entire should probably be deleted so LR can rebuild them. The previews folder is called catalogname Previews.lrdata and is a subfolder of where your catalog file (.lrcat) is stored. You can location your catalog by going to the General tab in the Catalog Preferences and clicking the Locate button. You should exit LR before trying to delete the Previews subfolder and make sure you’re not deleting the catalog or backups folder, just the folder with Previews.lrdata in the name.
If the Library view just shows a different-looking version of the LR adjustments then perhaps something is wrong with the display-driver or the monitor’s color profile.
The preview does indeed change. I don't know how to tell LR to recompute previews. That may have been my 'mistake' as I imported the original .arw (Sony RAW) images from the card using 'Copy as DNG' and used embedded and sidecar, as opposed to standard, for the previews. I changed that setting today, after this started happening.
I have deleted the previews folder, while LR was closed, but still have the same issue. It can't be the hardware, as I followed instructions from Adobe Support, about 2 hours ago, and set up a different user account. there was no difference between the library and develop images there, But, they were different images, I could not gain access to the original images, even though I set up the new account as an administrator.
So, still have the issue, though I've wiped appdata and my previews folder, but do not have the issue as a different windows user, but I imported the images there differently and created different previews.
See also this discussion (rather long). http://forums.adobe.com/thread/1028187?tstart=0
In library mode you are seeing an Adobe RGB preview while in Develop mode you are seeing a Pro Photo RGB rendition. The differences should not be huge, though.