Error when installing Watir for IronRuby

Ruby IronRuby
#1

I updated my gem for Ruby (Not IronRuby) to 1.3.5

C:\DevTools\IronRuby\ironruby\Merlin\Main\Languages\Ruby\Scripts\bin>ir
igem -v
1.3.5

C:\DevTools\IronRuby\ironruby\Merlin\Main\Languages\Ruby\Scripts\bin>ir
igem ins
tall watir
ERROR: While executing gem … (RangeError)
bignum too big to convert into Fixnum

Any ideas about the above error?