"File access denied" when generating scheduling debug

Hello.
I’m getting this “file access denied” error message each time I try to generate a debug file when scheduling. Scheduling works fine when I uncheck the “generate debug file” box.
I get this message on 3 different computers (2 on site, 1 remote) so I reckon this is not a simple rights issue.
I’m using version 6.3.24 build 4498.
Any ideas ?

Thanks