FireQuery thowing NS_ERROR_UNEXPECTED under certain conditions

Firebug Extensions
1

When you run the attached code in firebug console (or in regular script), FireQuery will throw a NS_ERROR_UNEXPECTED exception.

var a = $("<select></select>");
a.prop("disabled",true);
a.data("test","test");

Test System:
Win7
FF30.0 (clean profile)
Firebug 2.0.1
FireQuery 1.4.1
No other addons.