Here are a couple of methods to try out.
Method 1: JavaScript
Add the following script to the change event of each checkbox.
if(this.rawValue == 1)
{
NameOfCheckBoxToUncheck.rawValue = 0;
}
Method 2
1. Make sure both checkboxes have the same name
2. Set the Data Binding field on the Binding tab of the Object properties to Use global data.
3. Set the On Value to be unique for each of the checkboxes ie. On Value = Yes for the yes checkbox and On Value = No for the no checkbox.
The nice thing about setting up checkboxes to be mutually exclusive over radio button is you can deselect a choice whereas you can't deselect any of the radio buttons in the group. You can also tab through each checkbox unlike radio buttons where you tab to the radio button group and use arrow keys to cycle through each radio button in the group.