Cannot open standard form in Adobe Lifecycle Designer

Dear community,

I am despairing. I want to open the standard SAP form in Adobe LifeCycle Designer (ALD). Therefore I create a copy of the standard form, download this, extract it and open it with ALD. But then the error appears:

"Cannot load schema" - and the data binding is disappeared (nothing in tab: data view).

What can I do?? I have done this last week and it worked...and now I cannot even open forms with data bindings in ALD.

Please help me!

Warm regards,

Deborah