Straight to the questions:
1) You should customize the control templates (they are four) of the RadMenuItem and remove the corresponding backgrounds and borders. You could remove the icon area by setting IconColumnWidth=0 on RadContextMenu, but this will hide both the background and the icons, so I guess this is not what you want. You could check the following help article for more information:
2) Is this problem happening with the latest version of RadMenu (2011.3.1116)? This behavior depends on the commands that you use - the RadMenuItem keeps weak references to the commands' events and if the command implementation is also with a weak event it is possible the GC to collect the event handlers several seconds after the application is loaded. Probably a simple example project demonstrating the behavior will be the most helpful thing, but I suppose that more information will be enough - version of RadControls for WPF, delegate command implementation - Telerik, PRISM, MVVM light, or other MVVM framework, or own implementation?
the Telerik team
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