InfoPath 2010 At least one check box should be checked

Here is a simple solution for making one of the check box is checked before submitting the form

1. Create your checkbox fields (of data type true/false boolean)
2. Create a flag field and set default value to zero
3. Create a Submit Button
4. Create a message view
 
5. For each check box add 2 rules
6. Rule 1:  if checkBox1=true, Set flag = flag + 1


Rule 2: If checkBox1=False, set flag = flag - 1

 
7. On Submit Button Add 1 rule  If Flag=0, switch to message view



Hope This helps...