You are correct, it's not assigned unless a set of specific menu items are selected from drop down menus, however I've made sure to make those selections and I know that it's been assigned by using the debugger. The thread runs, fills the list, and then is somehow set to null.
I'm very new to C# Threading, so I'm learning a lot through this project. Our website was initially done in ASP.NET Framework 2.0, I've changed it to 3.5 but the server does not support anything above that, so now I'm looking through the multiple ways of accomplishing this and best practices. Currently going through "C# in a Nutshell" which has been great. Your suggestions are much appreciated.