Can't seem to get apps running in the simulator nor on iOS devices after TiSDK 3.4.0-rc4 Update

I have installed XCode 6.0.1 (the newest one which contains iOS SDK 8), and consequently installed the Ti. Studio 3.4 and Ti SDK 3.4.0-rc4, but now nothing works. I followed the instructions in the Appcelerator blog. This is what I get in the console:

[ERROR] : Failed to load command "build"
Please report bugs to http://jira.appcelerator.org/
[ERROR] : TypeError: Cannot call method 'map' of undefined
at Object.<anonymous> (/usr/local/lib/node_modules/titanium/node_modules/node-appc/lib/exception.js:33:27)
at Module._compile (module.js:456:26)
at Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Module._load (module.js:312:12)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at Object.<anonymous> (/usr/local/lib/node_modules/titanium/node_modules/node-appc/lib/auth.js:25:18)
at Module._compile (module.js:456:26)
at Module._extensions..js (module.js:474:10)
---------------------------------------------
at Object.run (/usr/local/lib/node_modules/titanium/node_modules/node-appc/lib/subprocess.js:59:8)
at find (/usr/local/lib/node_modules/titanium/node_modules/node-appc/lib/subprocess.js:96:14)
at q.process (/usr/local/lib/node_modules/titanium/node_modules/async/lib/async.js:731:21)
at processImmediate (timers.js:330:15)

It seems like node modules aren't playing nicely.

I have tried to reinstall Titanium studio and all that.... but still nothing. I have spend the whole day with this issue.

Is there a solution of this? If not, how do I revert everything to previous SDK?

Thanks for you help.