Thank you all for caring. I finally got LRC running. I uninstalled LRC completely and moved away any LR relating files except my lricat file. After re-installing everything was alright. Then efter some days I dived into some menus, edit setting I think, and LRC collapse again. I did as above once more. Now I am to scared to touch anything like the hints below, i.e. to switch off the GPU support. I did not yet have any valuable setting so no big harm done. I do need to get this sorted out so I can trust LRcompletely. I will study the all the hints below carefully before next attempt.
I am very happy to know that this LC community is active and answers quickly.