Gem error installing capistrano

[Bob Lehman]

Does anyone know what this error means and how I fix it ? Or some clue
as to how to debug it?

C:\Documents and Settings\Administrator>gem install -y capistrano
Bulk updating Gem source index for: http://gems.rubyforge.org
ERROR: While executing gem ... (Zlib::BufError)
buffer error

I get it on two different windows environments.

Any help is appreciated.
--Bob