I wrote you guys an email when 10.5.2 appeared, but you said it was fixed in 10.5.2. Okay it fixed the shadow problem. But there are many devs who used a trick to make the shadow look good even if Leopard was buggy. This is when the problem appears. The shadow is too far away from the text now.
I found this problem using the Stockholm and the Gone Dark theme. Both are default themes included with Adium. See the drop shadow under the time
See this for example of an app that resolved this problem http://culturedcode.com/things/wiki/index.php?title=Release_Notes
At the bottom you can clearly read what I'm talking about: "Fixed the drop shadow problem on Mac OS X 10.5.2"
I updated from .8 to .9 and the bug was gone. That was exactly the same problem that I am seeing right now in Adium (for a while now).