memcached and memcached-northscale

OK! conclusion:

a) Using memcached and memcached-northscale for
Rails.cache.write, it *always* returns false.

b) memcache-client works fine.

Nothing to do with Ruby 1.9.1, that's only because
I runs memcache-client in Ruby 1.9.1, [0]
after switching to memcache-client, everything is fine.

Not sure why Rails.cache.write returns false,
since it did really write the cache. And if you use
Memcached::Rails.new directly, it seems fine too.
So the problem might be combined with Rails and Memcached
with or without Northscale, they all suffered from the same error.

[0] Because both memcached and memcached-northscale didn't run
on ruby 1.9.1.

[1] Pure ruby is so much better. Stop using curb,
SystemTimer, etc, etc...