New Post: .Net 3.5 to 4.5 Conversion.

I Figured it out...

The problem wasn't related to the dlls or anything server side. For some reason, calling the __doPostBack on the onclick event embedded on an html control broke it.

<li runat="server" id="liExport" onclick="__doPostBack('ExportMyStuff', 0);" ClientIDMode="Static">Export Results</li>

I ended up wrapping the onClick call in jquery and everything works fine now.

$(document).on('click','#liExport',function () {
                __doPostBack('ExportMyStuff', 0);
            });