Thanks Ravensc for your help.
I've removed the preference file. Still doesn't work
Something strange : In my document library, I have 2 folders named "Resolume Arena 5" : 1 is empty, and the other has the "good" folders (composition, fixture library, preferences, presets and recorded".
I have this problem with my main PC (win 7) and my PC for the shows (Win 10 up to date). Both with Arena 5.1.4.
Here a zip file with the log file, the 2 config files :