I don't see any log entries related to sending notifications for your account.
Would you mind looking in Console and checking for any error messages related to Howl? You can filter by Growl or GrowlHelperApp to see any errors which might be caused by Howl.
You can also check to make sure that Growl is set as your default Display Style - or at least the Display Style for the notifications your are interested in.
If you'd like more help, please contact me off-list at sup...@howlapp.com.
Jon
Howl Developer
j...@howlapp.com