Well, I loaded 3.88 in my sandbox.

URL's are working for the product details.

I had to remove the Category module and re-instate it on the page with BuyNow and it is working.

The Featured Products module (not on the same page as BuyNow) throws a critical error (Object Reference not Set Error)

Category module not on the same page as the buynow module is blank; even though the BuyNow page is set in the settings.

Nope. That's worse. Now nothing is working.

A critical error has occurred. Could not load file or assembly 'App_SubCode_SmithCart, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.

Smith.FeaturedProducts

Error: Smith.FeaturedProducts is currently unavailable. DotNetNuke.Services.Exceptions.ModuleLoadException: Could not load file or assembly 'App_SubCode_SmithCart, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified. ---> System.IO.FileNotFoundException: Could not load file or assembly 'App_SubCode_SmithCart, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified. File name: 'App_SubCode_SmithCart, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' at Smith.DNN.Modules.FeaturedProducts.FeaturedProducts..ctor() at ASP.desktopmodules_smith_featuredproducts_featuredproducts_ascx..ctor() at __ASP.FastObjectFactory_app_web_j6jrec2v.Create_ASP_desktopmodules_smith_featuredproducts_featuredproducts_ascx() at System.Web.UI.TemplateControl.LoadControl(IWebObjectFactory objectFactory, VirtualPath virtualPath, Type t, Object[] parameters) at System.Web.UI.TemplateControl.LoadControl(VirtualPath virtualPath) at DotNetNuke.UI.ControlUtilities.LoadControl[T](TemplateControl containerControl, String ControlSrc) at DotNetNuke.UI.Modules.ModuleHost.LoadModuleControl() WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. --- End of inner exception stack trace ---

... I restarted IIS and my Database server... sam ting.