Rename your .lrdata folder. This will force Lightroom to create a new cache file, and Lightroom should start again for you. After you have things running again you can delete the folder that you rename.
Good afternoon Jim. I had the same problem:
"Lightroom encountered an error when reading from its previous cache and needs to quit. Lightroom will attempt to fix this problem the next time it launches."
Thank you very much for your recommendation. It worked great!
I've got the same problem. Renamed the file. Started Lightroom and had the same error message. New file created, deleted the renamed one. Still won't start!!!!!!!!!!!!!