I was away from komputer last day. Yes I have win 8.1 with all updates and MO 1.2.18. Today I was reading about new issue in MO -> https://issue.tannin.eu/tbg/modorganizer/issues/1014 I think it's exactly the same problem. I'll let you know when I figured it out...
Edit: OK, added process_blacklist.txt with steam.exe steamerrorreporter.exe resolved failure.
Thanks everybody, I appreciate your time and effort to help :)