Rules are only executed when an object is saved.
Could there be any exceptions to this by any chance?
In your object, check to see if there are any business rules that execute a process dynamically or not, with 'on initialisation' selected etc..
e.g If Object.Name is defined Then StartMyProcess
Do you have a rule that chnages the Yes/No attribute's (or other ypes) value and that attribute has the 'Save from when value is ticked/unticked' in the presentation?
Not sure what else would kill the modal window.
Cheers