We have multiple orgs using ForceTK to call ApexRest services from VisualForce pages. Everything has been working just fine until last night. Now none of our calls are going through:

XMLHttpRequest cannot load https://cs41.salesforce.com/services/apexrest/v1/productmarkets/. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://c.cs41.visual.force.com' is therefore not allowed access. The response had HTTP status code 401.

We've added the CORS records to the org with no difference in outcome. I understand that this is more than likely not a ForceTK issue, but something that has changed on the Salesforce side. I'm wondering if anyone might have suggestions on things I can try to get this to work?