Problem with gem update.

Im trying to update my gems with

sudo gem update --system

and im getting this error.

Updating RubyGems
WARNING: RubyGems 1.2+ index not found for:
  http://merbivore.com

RubyGems will revert to legacy indexes degrading performance.
Updating metadata for 120 gems from http://gems.rubyforge.org/
........................................................................................................................
complete
ERROR: While executing gem ... (Gem::RemoteFetcher::FetchError)
    bad response Not Found 404 (http://merbivore.com/Marshal.4.8)

What do i have to do fix this and complete an update?
Why is it giving me that merbivore reference?

Hi,