I have a transfer which keeps failing due to the connection being dropped by the ftp server. When notification of it is posted to growl, duplicate notifications are posted. The first time since launch, one is posted. Then each time it fails after that, one more is posted. The attached screenshot is of the 20th time the transfer failed since launch. And no, I don't have growl leaving notifications up, all of those popped up at once with one failure.
We will udpate to the latest Growl version in 3.0.1 and this may fix the issue you see. Cannot replicate this myself. Please try the latest nightly build from (http://update.cyberduck.ch/nightly) which already includes version 1.1.2 of the Growl.framework.