When attempting to set an estimate by clicking on the "Current Estimate" column in a listview in my On Demand account (dandoes.fogbugz.com), I see the following JS error show up in FireBug when clicking on the link:
Syntax error, unrecognized expression: [tagName=FB:EST]
This happens regardless of whether an estimate is already set.
I am running Firefox 5.0 on Win7/x64.
I also see the same error in Chrome 13.0.782.55.