Thanks for your reply Chetna Srivastava... I disabled "show add photos screen"... to no avail. Performance still ranges from glacially slow to non-responsive...
Open to other suggestions, if anyone has any.
FWIW, Bridge and Photoshop still appear to work just fine.
I too have found LR to act weirdly and finally found that it only does it when I have WiFi turned on. It won't open photos or it will open a landscape shot in portrait format, it locks up and I have to force shutdown or it just crawls. Sometimes it will jump ahead to a photo all by itself. Turning off WiFi and all is well again. Strange behavior for sure.