Lightswitch: cannot fill form

I followed tutorial here http://blogs.msdn.com/b/jasonz/archive/2010/08/23/lightswitch-beta1-now-available-building-your-first-app.aspx#comments

The form runs but I 开发者_StackOverflowcannot fill it ! Why ?

Update: There's no error message I just can't enter the field to type anything: it's read-only

Update 2: I ask the gurus on Microsoft Forum, they tried to answer hard, nobody can find out why. Seems beta is very beta :)

Weirdly I did have this problem on a windows 7 PC not on a Windows 2008 pc

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Try these,

1) Have you selected the Editable Grid Screen ? 2) Is there any add new icon on the top right corner of grid screen you can click to add new items into?