respond_to js with render :layout => false segfault

A little convoluted but I have the following code sequence.

JS/jQuery calls

$.get(uri + "/update_status", null, null, "script");

which is defined as:

def update_status
 @sites = Site.all
 PingWorker.async_ping_all_sites
 respond_to do |format|
  format.js { render :layout => false }
 end
end

which is supposed to render

- @sites.each do |site| 
 - if site.status == "dead" 
  jQuery('#block#{site.id}').removeClass("green")
  jQuery('#block#{site.id}').addClass("red")
 - else 
  jQuery('#block#{site.id}').removeClass("red")
  jQuery('#block#{site.id}').addClass("green")

Which in return, gives me a segfault and kills my Mongrel instance.
I am using 3.0.0pre edge, ruby 1.9.1.

The only other thing I get is from firebug which shows a xml response of:
XML Parsing Error: no element found Location: moz-nullprincipal:{7a8e232a-7979-da44-8d55-22a592fcbfb5} Line Number 1, Column 1:
^