SAS default behavior is to overwrite log-files etc. Are you sure that the previous SAS process has ended or that any other process/program (Notepad etc) is not locking the log file? Are you using the same user account? What user rights error message do you get?
Typically, these kind of problems needs to be solved at the site by testing different thing, in order to narrow dow the problem, like testing different input programs, start from different directories, using different user account...
In problems regarding user rights, maybe the Windows server administrator can help.
Regards,
LiInus
Data never sleeps