Why Lifecycle Designer ES4 crashing on a pdf form created in ES2

On HP Probook 4730s laptop with Windows 7, Designer ES4 keeps crashing on a pdf form created in ES2. Opening it in Adobe Acrobat Pro XI and reader is fine. Installed the ES4 sp1 did not help. Other forms are fine. No special fields on the form except some basic textboxes, signatures, checkboxes, lines.

Any idea about how to fix this?

Thanks