gem update --system が終わらない

数か月ぶりにRubyを触ろうと思って、gem を update しようとしたらハードディスクががちゃがちゃ言い続けて戻ってこない。-V してみたら

$ sudo gem update --system -V
Updating RubyGems...
missing 17836 gems
Bulk updating Gem source index for: http://gems.rubyforge.org
ERROR:  Unable to fetch Marshal.4.8.Z: invalid Gem::Specification format
 ["1.3.1", 3, "flow", #<Gem::Version "0.0.1">, Sat Aug 09 07:00:00 +0900
 2008, "A Web Server", #<Gem::Requirement:0xb5ad5948 @requirements=[[">=",
 #<Gem::Version "1.9.0">]], @version=nil>, #<Gem::Requirement:0xb5ad5790 
@requirements=[[">=", #<Gem::Version "0">]], @version=nil>, "ruby", 
[#<Gem::Dependency:0xb5ad55ec @name="rev", @type=:runtime, 
@version_requirements=#<Gem::Requirement:0xb5ad5588 @requirements=[[">=", 
#<Gem::Version "0.2.2">]], @version=nil>, @version_requirement=nil>], "flow", 
"ry at tiny clouds dot org", ["ry dahl"], "A Web Server", 
"http://flow.rubyforge.org", false, "ruby"]
Ctrl-C
ERROR:  Interrupted

なんだこりゃーと思って調べたら、とりあえずFAQに載ってた

3.2 RubyGems hangs while updating the source index.

I have a problem with RubyGems. It doesn’t matter 
what I try to install with, it freezez.
Particulary I tried to execute:

   $ gem install rails --include-dependencies

but the command freezez at the following message:
"Updating Gem source index for: http://gems.rubyforge.org"

Answer

[I lost my internet connection while composing the 
 answer to this question. Unfortunately, I now no 
 longer recall what I intended to write. The answer 
 (or at least part of the answer) is buried deep in 
 the RubyGems mail archive. I’ll try to update this 
 after a bit of research. Sorry for leaving this 
 question hanging.]

ちょ

もう少し調べる。