I just ran across this today. There is a bug with required checkboxes in CFMX7. Basically they don't work. However, you can get around this by simply writing your own validation using onSubmit. This is a known issue so no need to bug MACR about it. This code block demonstrates the bug:

<cfform format="flash">

   <cfinput type="checkbox" name="agree" label="I Agree" required="true" value="1">
   <cfinput type="submit" name="submit" value="Push the button">

</cfform>

And here is a sample of how to fix it:

<cfform format="flash" onSubmit="if(!agree.selected ){ alert('You must agree!'); return false; }">

   <cfinput type="checkbox" name="agree" label="I Agree" required="true" value="1">
   <cfinput type="submit" name="submit" value="Push the button">

</cfform>