ShDocVw.dll Issue

I am having a strange issue. I have an .NET class library application which references the Microsoft Web Browser control, shDocVw. dll located in the System32 folder. When I integrate my library into another main application that already has the Interop DLLs created by an earlier reference, navigation to the browser gives error saying that Navigate2 method was not found. If I then update the Interop DLLs with the one created in my build path or the bin folder, everything works fine. I noticed that the main application DLLs have timestamp of April whereas my System32 dll and hence the Interop dlls have a timestamp of May. Does this mean that because I am probably referencing an updated version of the DLL, the navigation doesn't work with the older files? Do I have to update any client machine using the application with the updated Interop DLLs in order to get everything working smoothly. Or can I replace my system dll with the same version that was used for the main application and then try? What would be the ideal solution? Any answers?