To follow up, adding this line to the gem spec fixes the problem:
s.platform = Gem::Platform::RUBY

I noticed a couple other gems have been affected by this:
"addressable-1.0.1.gem"
"gchart-0.1.0.gem"

Dan

On Dec 10, 10:14 am, Dan Manges <daniel.man... / gmail.com> wrote:
> Has anybody released a gem built with rubygems 0.9.5?  I built the
> latest version of deep_test with 0.9.5, but it seems like it cannot be
> installed with 0.9.4 clients.  It shows up in the gem list without a
> platform (version 1.0.3):
>
> Select which gem to install for your platform (i686-darwin9.0.0)
>  1. deep_test 1.0.4 (ruby)
>  2. deep_test 1.0.3 ()
>  3. deep_test 1.0.2 (ruby)
>  4. deep_test 1.0.1 (ruby)
>  5. Skip this gem
>  6. Cancel installation> 2
>
> ERROR:  While executing gem ... (OpenURI::HTTPError)
>     404 Not Found
>
> It's then looking to download the gem with an extra hyphen at the end:
> "http://gems.rubyforge.org/gems/deep_test-1.0.3-.gem"
>
> I submitted a defect, but wanted to know if anybody else ran into
> this.http://rubyforge.org/tracker/index.php?func=detail&aid=16177&group_id...
>
> The gemspec I used is here:http://deep-test.rubyforge.org/svn/trunk/Rakefile
>
> Thanks,
> Dan