I just upgraded to snow leopard. Before, I had everything running fine, but now when I start the server from the terminal I get:
=> Booting WEBrick
=>
I just ran into this problem. This is what I ended up doing:
rm -fr ~/.gem
sudo gem install rails
sudo gem install sqlite3-ruby
Now my rails/sqlite3 app is running again.
sudo port install sqlite3 sudo gem install sqlite3-ruby
Another possible cause for this problem is continuing to use Ruby versions installed with rvm (http://rvm.beginrescueend.com/) on Leopard after upgrading to Snow Leopard.
Ruby versions installed with rvm are built from source and needs to be reinstalled on Snow Leopard to work with the sqlite3-ruby gem.
I've done all this... the only thing that has worked for me is
sudo env ARCHFLAGS="-arch x86_64" gem install sqlite3-ruby
Note: I did have XCode installed from devloper.apple.com, not the CD. The CD install of XCode Tools did nothing to fix this problem for me.
If you don't have any XCode installed, you may need to get XCode 3 or 4 from http://developer.apple.com/xcode. You will need to sign up for an account. Presently, you may download XCode 3 for free without paying the $99 annual fee.
You should re-install XCode from the Snow Leopard DVD. This should fix the linkage problem!
if you install the UNIX Dev Tools from the XCode installer, this should include the necessary header files (ruby.h).