InRule will periodically read and write to the temp directory. Therefore the user account which the app domain is running under needs to have sufficient permissions to the temp directory, so that it can read/write files and directories.
The temp directory used will be whatever %TMP% is set to, which may depend on whether the account has user environmental variables:
If you are running InRule from an application managed by IIS, then the user account will be the identity of the application pool. Therefore, you need to assure that the account has full access to the temp directory, or you can grant ‘Everyone’ full access, as shown below: