As I was writing this I got the solution, but having spent the time decided to share....

User reports that cannot view work items.  I've pinned it on Defect work item type.  Inspecting the presentation and binding look reasonable.  But in Firefox I get a JavaScript error "TypeError: _e[_d[i].slot] is undefined"
Tracing in WebConsole get's to this section

var _e={"details":[],"linkSummary":[],"quickInfo":[],"defaultSection":[],"description":[],"discussion":[]};
for(var i=0;i<_d.length;i++){
_e[_d[i].slot].push(_d[i]);
}

It turns out there was an empty Section under the Overview tab.  I removed it, saved and now I can load/view defect work items.