Hi,
Sadly I do not have a copy of the older version of threads installed now. (I would recommend upgrading
)
However within the control panel, you should fine a box to enter the path to store an admin log file.
The folder that you enter at this location should be writeable by the server. I believe there is also a check to see if the directory or folder is writeable.
If someone has the exact location within the control panel, I am sure they will post. But if you go through each option in turn you should find it easily