What are .C1 and .C2 Gerber files in Altium 14?
I ran into this also this morning - turned out to be the export from camtastic to gerber setting "Separate Composite layers to individual files" checkbox.  It should NOT be checked:



To get there, have the Camtastic file open and go to menu File => Export => Gerbers

Note that I had to save my project in AD19 for the changes to work.