[YAML] allocator undefined for Bignum

[Une bévue]

in a yaml file i do have "Time.new.to_i" and get the following error for
those fields :

TypeError: allocator undefined for Bignum
method transfer
in yaml.rb at line 133
method load
in yaml.rb at line 133
at top level
in org.ytho.MacSOUPSwitcherWatch-0.3.rb at line 86

on MacOS X (latest) using ruby 1.8.4, the line 86 of my code being
simply :

@prefs=YAML::load(File.open(@h['PREFS_FILE']))

(reading back my prefs ssaved as a yaml file)