Just click one of the announcement posts on top of every Sencha Touch forum page:
This solution is better than the accepted answer. Copying the sdk folder is redundant: It's still there, has simply been renamed to "touch". So thank you for this.
Originally Posted by jgarifuna
Still, this seems like a somewhat suboptimal situation, as it prevents out-of-the-box creation of a working Sencha Touch Hello World application. Hope it gets fixed in the next beta.