I have the same problem, I have just set up my panel styles, draged them to a tool palette and all is fine until I try and insert one of the new panels. Crashes MEP 2009 every time. I can insert the original panels and I can change it to one of the new styles using properties, no problem.
I created the new styles by copying an existing style and changing the plan and model view blocks to represent our standard symbols and the size of panel we are using.
Be great if it worked, but it crashes every time.