InfoPath Dev

I found something really strange - - (btw - I'm using 2010)

when I preview this form - - all the rules work well (when checkbox=false, then dtp is not enabled).

However, when I publish the form, the DTP itself doesn't work. In other words, when I check the checkbox - I can't select a date from the DateTimePicker. I can type in a date, it's just that the dropdown calendar doesn't work.

Then, when I uncheck it, the DTP dims out (like I would expect a disabled control to look) . Of course, it doesn't work then either.

yes it is

Please check the postback settings on the controls that have rules that execute in the browser.

You'll also want to test on another machine to make sure that it's not an Internet Explorer issue blocking the date picker functionality.