Have been running DNN for over two years now on corporate intranet, followed upgrade paths every now and again, running on 4.8.2 (have been since it first came out).  All of a sudden and for no apparent reason our Text/HTML modules all ceased to function just now with the following error:

Error:  is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: The type initializer for 'DotNetNuke.Modules.HTML.DataProvider' threw an exception. ---> System.TypeInitializationException: The type initializer for 'DotNetNuke.Modules.HTML.DataProvider' threw an exception. ---> System.InvalidCastException: Unable to cast object of type 'DotNetNuke.Modules.HTML.SqlDataProvider' to type 'DotNetNuke.Modules.HTML.DataProvider'. at DotNetNuke.Modules.HTML.DataProvider.CreateProvider() at DotNetNuke.Modules.HTML.DataProvider..cctor() --- End of inner exception stack trace --- at DotNetNuke.Modules.HTML.HtmlTextController.GetHtmlText(Int32 moduleId) at DotNetNuke.Modules.Html.HtmlModule.Page_Load(Object sender, EventArgs e) --- End of inner exception stack trace

I have restarted IIS, recycled the app pool, restarted the server and the error persists.  There have been no changes on that server (dlls, otherwise) in over a week.  What the heck just happened?

I "fixed" it (have no idea why my "fix" worked).  I went into the web.config and converted it to use asp.net 3.5 (again, this shouldn't change anything but I was desperate and just grasping at straws).

So converting my DNN installation to use ASP.NET 3.5 fixed it.  This is not on a Vista machine, not using IIS 7.  We run on Windows 2003/IIS 6.

Any ideas what happened would be greatly appreciated... and why the heck a web.config edit would fix it when restarting IIS, app pool, and server didn't do jack.  Maybe cached files that didn't go away when they should have?