I'm using Ubuntu 12.04, but the following problem occurs on Windows 7 as well.
I've stumbled upon a somewhat strange problem: I've downloaded and installed Sencha 18.104.22.168 properly, and smae for the SDK. I can create a project (e.g. "sencha generate app GS ../GS"), but It isn't shown properly on either Chrome or Firefox.
In Firefox it doesn't display any graphics, and looks nothing like the examples in the first tutorial. On chrome, the loading screen is stuck, and I cannot proceed further.
I should mention that I'm not using a local-host to open the project, I just open the index.html file directly from FF/Chrome.
Edit: After installing an apache server on my system, it works okay with chrome, when opening the app through the address "localhost/GS". Firefox still behives weird, though: