Good news, my problem is solved, everything works fine now.
I tested the program in safe mode and found it worked ok.
Could be deduced that the problem was caused by one of those third-party application that load automatically at startup or login.
And, by elimination, I came to discover the culprit: module DrivePulse of Drive Genius.
I also found on the Apple forum, someone struggling with the same problem. And in his case, the application Logmein seemed to be involved.
In conclusion, let's say it would be appropriate to beware of all these programs running in the background.
Many thanks.
I tested the program in safe mode and found it worked ok.
Could be deduced that the problem was caused by one of those third-party application that load automatically at startup or login.
And, by elimination, I came to discover the culprit: module DrivePulse of Drive Genius.
I also found on the Apple forum, someone struggling with the same problem. And in his case, the application Logmein seemed to be involved.
In conclusion, let's say it would be appropriate to beware of all these programs running in the background.
Many thanks.