Node.js: Error: Cannot find module 'stack'

I tried to install howtonode.org on my Osx

cd ~/Sites/
git clone git@github.com:creationix/howtonode.org

My context is the following:

OSx version: 10.7.4
node -v v0.6.15

When I try to run the following command

~/Sites/howtonode.org node server/server.js &

I get the following error:

node.js:201
        throw e; // process.nextTick error, or 'error' event on first tick
              ^
Error: Cannot find module 'stack'
    at Function._resolveFilename (module.js:332:11)
    at Function._load (module.js:279:25)
    at Module.require (module.js:354:17)
    at require (module.js:370:17)
    at Object.<anonymous> (/Users/antoniopierro/Sites/howtonode.org/server/server.js:2:13)
    at Module._compile (module.js:441:26)
    at Object..js (module.js:459:10)
    at Module.load (module.js:348:31)
    at Function._load (module.js:308:12)
    at Array.0 (module.js:479:10)

[1]+  Exit 1                  node server/server.js

any ideas?