JsonRestStore failure in Firefox 3.6

[parente]

Logged in, posting a new user / role pair to the AccessUsers collection.

invalid 'in' operand _26
[Break on this error] window[(typeof (djConfig)!="undefined"...ll;};_6.json.ref._useRefs=true;}}};});

JsonRestStore.xd.js (line 8)

Not sure what's at fault yet.