take a lookon this may it help
http://msdn.microsoft.com/en-us/magazine/bb985026.aspx

 Hi All

I am trying to strong name kcommon.dll which is 52kb in size . After strong naming through sn.exe , i am in trouble . The asssembly is now 42kb in size and some of the overridden methods are lost and i m also !
Can any one please help about what is going wrong.