We're seeing this on Windows 2003:
Argument 'cnf' requires additional parameters. Error: The parameter is incorrect.
The comments in the script seem to indicate this parameter was removed at one point for 2003:
# - Removed -cnf option for Windows 2003 based servers since the logs would run continuously. Log roll is disabled. Maxsize or duration is used, whichever one comes first
But it's still there in at least some cases:
#Windows 2003 (Removed duration since log roll fails to work with duration specified)
$commandString = "logman create counter -n Exchange_Perfwiz -cf Exchange_Perfwiz.Config -s $ServerName -f bin -cnf -max $maxsize -si " + $interval + " -o " + $filepath + $ServerName + "_" + $rolenames + " -v MMDDHHMM"
Unfortunately I don't have my own Win2k3 server to test on at the moment.