steps to reproduce:
Download tree from git, Date: Thu Sep 24 13:45:43 2009 +0100.
Get the audio plugin project compiling as AU.
Run in Logic 8 on OS 10.5.6.
Click on any component in the plugin window, or in the plugin window background.
After clicking in the window, rolling over components does not highlight them. This condition persists until the plugin window is closed and opened again.
This problem does not show up in AU Lab.