I have a simple application with 3 dockable panes:
After each docking iexplore.exe process memory increases and never decreases.
I inspected iexplore.exe process using YourKit profiler. And noticed that every redocking results in creating new instances of RadPaneGroup, RadPane, DragValidator, PaneHeader, RadButton etc. These instances are never garbage collected.
Many redockings may result in great memory leak.
P.S. There is memory leak in silverlight when using inline DataTemplates http://forums.silverlight.net/forums/p/171739/415825.aspx. Maybe this is the issue.