I noticed application window cannot be restored from the tray icon sometimes. This happens regularly since recently. Task manager shows the app consumes 25% of CPU in such cases while memory usage is just 33 MB instead of normal 100. I started to share big amount of files (150 GB) recently - probably that is the case, not sure.
I could send a report but there is no crash :)
Client version 10/18/2011, Windows 7 Home Basic SP1