I've have been working on a form where specific fields are required, however depending on which options you select, some fields become not-required.
For example, New Client v.s. Change to a client.
If the user clicks the check box beside "Change" to a client, the required fields under "New" Client become disabled and vice versa.
fieldname.mandatory = "disabled";
Check if you have any hidden fields on the form which are required..
If not, some how the disabled may not be working as expected..
If you still have issues, you can send your form to LiveCycle9@gmail.com so I can have a look at it..