I have narrowed it down to a conflict between private internet access and calibre. Whenever PIA is running (vpn program) calibre either fails to start or will take multiple tries to start and even then it starts slowly. When PIA is not running then calibre runs fine.
PIA says no comment and no one else on their forums has any concerns with running programs alongside it.
I have tried different (32 and 64 bit) versions of the VPN and they all work fine but calibre has the problem with them running.
https://www.privateinternetaccess.com/pages/download