Since ListBasedWebPart is the base class for the cascading menu web part, not seeing it in the intellisense off "using" statement is correct in your VS.NET file. Am I right by assuming the screen shot illustrates your code behind file for your custom master page? It seems to me that you are able to declaratively include qCascadingMenu in master page using SPD 2010 but failed if you are programmatically including it in the master page code behind in your VS.NET solution. Please clarify if this is the case.
If that is the case, with "using WA.Common" is not good enough. You will need "using WA.Navigation" and add WA.Navigation.dll to project reference. This assembly contains the "CascadingMenu" web part.