We're looking into this at the moment! I'll keep you updated.
Edit 1: We've created a potential fix and we're just about to test it. If that goes well we will push it to the live realm.
Edit 2: The test went well. New patch incoming!
Edit 3: The new Steam patch is now available. Stand alone patch still coming.
Edit 4: You should now also be able to patch on the stand alone client.
Edit 5: Please ignore edit 4 and forgive me. Still waiting on the stand alone client patch.
Edit 6: The stand alone patch is now live. If you're receiving the "In source code file:" error on Steam can you please let us know when this happens?
Edit 7: The shader error appears to be fixed now but people are still experiencing the "In source code file:" on both the Steam and stand alone clients. We're investigating this now. Thank you for your reports.
Edit 8: We're opening the queues while we investigate this. It seems that you can click past the error but we will st...