Strange Error wrt Enabling 32-bit Applications

I was trying to resolve an issue related to Crystal Reports not running properly in the deployed version of my app.  So I followed some suggestions, went to the IIS Application Pools, and changed one Advanced Setting in .NET v4.5:    Enable 32-Bit Applications = True
I stopped & restarted IIS to ensure the change had taken effect.  When I reran my application in the browser, I got a very strange message on this line of my code:
ScriptManager.RegisterStartupScript(page, page.GetType(), Guid.NewGuid().ToString(), "alert(" + Tools.EncloseInSingleQuotes(msg) + ");", true); The message was this: "Object reference not set to an instance of an object."
Why would enabling 32-bit applications cause this to happen?
Note: As soon as I set it back to False, the app started fine. Robert