Sleep Issue / Help with Rule?

Hi, just trying out Hazel for the first time.
I set up a rule to watch my Downloads folder for certain files and then move them to my Dropbox automatically, and to provide a Growl notification upon completion of the move.
With this rule in place both of my macs (MBP & Mac Pro) refuse to sleep. I achieve display sleep but system sleep is a no go.
Removal of Hazel allows my computers to sleep again. Am I missing something in terms of the way the rules are set up or is this simply one of the drawbacks of using Hazel to monitor a folder?
Cheers
Mustard
I set up a rule to watch my Downloads folder for certain files and then move them to my Dropbox automatically, and to provide a Growl notification upon completion of the move.
With this rule in place both of my macs (MBP & Mac Pro) refuse to sleep. I achieve display sleep but system sleep is a no go.
Removal of Hazel allows my computers to sleep again. Am I missing something in terms of the way the rules are set up or is this simply one of the drawbacks of using Hazel to monitor a folder?
Cheers
Mustard