Diary function after having used CTRL BREAK

We were running a program but stopped it using CONTROL BREAK. When we now want to restart the program we immediately get the following error message after the command diary('log.out');

Error using diary log.out: Cannot open file: permission denied.

After the message we have tried to exit MATLAB and restart it. However this does not help.

We have also changed the names of the files everywhere. Thus it is not a matter of naming.

We would be very grateful for some help. Many thanks in advance,

Wilko