Document.save() returns error "Failed to find any class definition for com.adobe.indesign::" in CS6

Hi all,

I am writing extensions in the InDesign 5 development environment (still)  - Extension SDK 1.5, Flex 4.0, etc., using ActionScript.

The extension works fine on InDesign 5 and 5.5. However when used in CS6, on certain computers (I can't find the common denominatior), when I try to save an open document using the document.save() command, Adobe often throws the error "Failed to find any class definition for com.adobe.indesign::" I.e., the name of the missing class does not appear - just the namespace com.adobe.indesign.

I'd appreciate suggestions what to do.

TIA,

mlavie