Hi Lorien,
I was able to produce the problem on my machine and fix the bug. I will be making a new release next week, but if you are working with the source code you can fix it in Web/Components/mojoProfilePropertyDefinition.cs, just uncomment the line of code at line 553:
datePicker.ID = "dp" + propertyDefinition.Name;
Thanks for reporting this.
Best,
Joe