Let me take some of that last message back.

When I access my online site which is still running 7.06 I can find no reference to nunit framework. It is only on my localhost as I test the upgrade on localhost version of that same website that I get the error. I haven't upgraded the live site until I can get it running safely here on localhost. Is it possible that there is something running here that is not running on the live site that causes the call to nunit.framework.

Paul

Hi,
I have checked all is up to date. I have even set it up on another machine running windows 7 rather than windows 8 on my normal testing machine.
I have noticed that on a couple of occasions I have had "Object reference not set to an instance of an object." with no reference to Nunit, but if I place just the Nunit.framework.dll in the bin folder all works as expected. I can't get to the bottom of it. I have removed skins and a number of modules but still the same error.
Thanks for the replies.
Paul

I recently upgraded a substantial website from DNN 4.9.4 to 7.1.2 taking the recommended steps along the way. Everything went well enough up through DNN 6.2.9. Then I made the jump to 7.1.2. The website started fine and the user-facing pages worked fine. However, when I tried to access Admin > Site Settings or Host > Host Settings, I would get the same:

System.NullReferenceException: Object reference not set to an instance of an object. at DotNetNuke.UI.Containers.ActionButtonList.get_ModuleActions()

error and exception described in the original post.

I too found that putting "nunit.framework.dll" (from nunit.org) in the "bin" folder of the DNN installation solved the problem.

Next, I tried to find which module was referencing nunit. "Dependency Walker" (depends.exe) was not helpful. Then I tried an oldie but goody DOS command in the "bin" folder of the installation:

find "nunit" *.dll

This reported that "gcheckout.dll" contained the string "nunit"!

Doing a:

find "gcheckout" *.dll

came up empty. So I don't know which, if any, module uses or references "gcheckout.dll".

Does anyone know which module or product installed "gcheckout.dll"? It could be the now-unavailable "Active Purchase" from "Active Modules", but I'm not sure.

Finally, I deleted (well, actually moved elsewhere "just in case") "nunit.framework.dll" and "gcheckout.dll" and the site is still working fine. So in the end, deleting "gcheckout.dll" was my solution.