Would suggest you to disable the option to use the graphics processor within Lightroom preferences> Performance
and then, do a fresh import to test.
If possible, share a screenshot of the Library module after import for further assistance.
Do you have "Apply auto tone adjustments" checked? (Preferences->Presets). Turn that off. There appears to be a bug in the auto tone adjustments in the latest LR that makes it apply strong negative exposure to all images upon import. Any images you already have imported will have this issue.
Thanks for the replies. I turned off both the "Graphics acceleration" feature as well as the "Auto adjustment", made a new catalog and re-imported. That seems to have done the trick. Thanks again.
Glad to know you got it working.