After choosing View QSO from the log list and then in the QSO window pressing Ctrl+F2 for New QSO, sometimes (always?) the Callsign field is read-only, i.e. I can't type a new callsign in there.
The only solution I've found is to restart CQRLog. So now I avoid using the "View QSO" feature.
73, Thomas M0TRN
In my case I simply hit "Escape" twice on the keyboard after viewing the QSO.
From that moment on I am ready for a new QSO.
The viewed QSO will not be deleted if you saved it first so no worries.
73, Tjalling PA3GOS