I\'ve just upgrade my rails application from the 3.0.7 version to the release candidate 3.1.0 and I got a strange error located in my atom feed builder:
Builder 3.0 is not compatible with fast_xs 0.8.0 on ruby 1.8.7 and will give this error. Perhaps you have that installed? (also note that Hpricot bundles fast_xs 0.8.0)
(edit:) you can monkey patch it by dropping this in your config dir:
class String
def fast_xs_absorb_args(*args); fast_xs; end
alias_method :to_xs, :fast_xs_absorb_args
end