Clicking on new item link on a list for most of my lists are showing popup but one of the list, which actually is exact copy of other lists, shows new item form in full window instead of a dialogue. I checked list settings and the new form in dialogue option is set to "YES". Any other idea? Any help is greatly appreciated.
Are you trying to create a "New Form" in the Dialog, from the "Standard View"?
Because in SharePoint OOB, the option "Launch forms in a dialog" is applicable only for the "Standard View".