Hi GoldingD Yes there was a lock file associated with catalog file. So deleted and retried with no success (even after reboot and multiple attempts etc). On execution of LrC to start program, new lock file is created. Lightroom appears in Task Manager as a background process (which presumably is not normal). And within approximately 60 seconds the computer freezes preventing any interaction at all. I have even attempted to end the process before freezing and can't do that either. This freezing does not occur with any other program and all works normally. But after starting LrC then freezing follows.
Would appreciate any assistance from you or the community with next steps to resolve this painful problem. Thanks in advance.