Hi.
Hope this isn't a known bug, I searched but didn't find anything...
This bug is easy to reproduce.
1. Install Quicksilver and their iTunes Module. This provides a Growl notification for track changes.
2. Set your notification to the Smoke theme.
3. Have some notification happen (i.e. an Adium message, etc, etc.)
4. While this notification is still on-screen, play a song with a long artist/album name. This then wraps to a second line*.
5. Have another notification pop up. It will then display beneath the iTunes notification. By this time, this notification should be three blocks down.
6. Skip to the next track once the very first notification disappears and iTunes' old notification is the topmost one (i.e. have iTunes notification refresh itself, since it does not ever display twice.)
The next time you get a notification, it will display moved downwards, just where the iTunes notification came up last time. By fiddling with this sequence, I got it to move all the way down and off my screen. I was able to reproduce this easily.
The only way to get the notification back into the line it's meant to be is by restarting Growl.
This isn't exactly a serious bug, but you'd be surprised at how often this kind of thing happens when you're chatting with someone and skipping ahead in your tracklist.
* I noticed it while playing "Ten Speed (Of God's Blood and Burial)" by Coheed and Cambria. It's on the album called "Good Apollo, I'm Burning Star IV, Volume 1: From Fear through the Eyes of Madness." Go figure.
mke.