It sounds like a permission issue. Try redirecting the stderr as well:
schtasks.exe /query /tn "repost_labor" 1> d:\scripts\labor\scheduled\repost_labor.txt 2>&1 to see if that puts any errors in the file (I think I've got the redirection correct :P).
The return value of 1, is likely an error. Apps should be returning 0 on success, but there's nothing error message wise to tell what's going on.
header('HTTP/1.1 420 Enhance Your Calm');