Prompt page, cascading and render variable

[Tsunami]

I have two reports.  The prompt page format appears to be identical, however, one behaves differently.

On both reports, I have a radio list box.  Depending on what your choice, a new set of more detailed prompts will appear.

On Report #1, I can make a selection, it will 'Auto submit' and will render the next prompt via render variable.  On report #2, when I make a selection, the 'Auto submit' will run the entire report instead of rendering the next prompt.  The only way I can get report #2 to behave the same way is to designate a 'Cascade source' under the properties of the sub prompt.

I currently have both reports open and have compared both properties and they are identical.  However, they are not behaving the same.  What am I missing?

Please advise.   

[ShwetalM]

if you attach both the report specs I could help point out the differences for you....
(while in Report Studio...Click Tools>Copy report to clipboard...open a notepad and paste...)