Thanks... You were right about one thing...  There was indeed an extra reference that would have ended up being recursive once the assembly was compiled into the web site.  For some reason I had apparently added a reference to the Membership provider.  I don't know why I would have done that since that provider relies on this one - but it is fixed at any rate.

However, even though the recursive reference has been removed, the problem still exists at the same line for the same provider.  Argh!  I am pulling my hair out over here...  :(

I also went through both project files side by side to ensure they were as identical as possible.  Now, the only differences are the Assembly Name and version number.  (I had also found a extra imported namespace "System.Collections.Generic" that has been removed.)

Does anyone have any more ideas?

Okay folks... Are you ready for a new symptom that I overlooked?  When I originally created this class, I named it "MyCompany.Providers.MyCompanySqlDataProvider" (substituting MyCompany of course).  However, I soon realized that my namespace was already "MyCompany.Provider" (not plural).  So, I changed it for the obvious reasons. 

(I stated the previous to say this...)

I was reminded of the old namespace when I double-checked the bin for any extra builds that shouldn't be there.  I didn't find a previous or conflicting build, but I did find the XML comment file in there with the OLD namespace.  So, I deleted it.  When I rebuilt the DLL, the XML file was recreated with the WRONG namespace.  What would cause that? 

The XML comment file does NOT match the namespace in the class file, so the compiler is doing something weird...

I also just checked the DLL in Reflector and the correct namespace is indeed generated for the DLL.  Has anyone heard of such a thing???