Cause:
when you restore you site collection on another computer or suddenly when you click on link to open your custom infopath form and mesage appear like:
The form cannot be rendered. This may be due to a misconfiguration of the Microsoft SharePoint Server State Service. For more information, contact your server administrator.
Solution:
Open up Central Administration
Go to Application Management
Under Service Applications click Configure service application associations
Click on the Application Service Proxy Group (2nd column) of the WebApplication you're trying your form on
Make sure the checkbox in front of State Service is ticked
Click OK and try your form again!