"CS6 Problem using Canvas Size: Re-written" Mon 28-Jan-13 04:40 AM by jerry r
If you have been using Nik Viveza and then try to use Canvas Size to put a border around your image you need to still have the Background Layer. You must be sure that in flattening and/or merging layers that you keep the original Background Layer. Re-naming the layer later as Background didn't help.
I found that to save storage space I was only saving the Viveza layer and deleting the Background layer, since the Viveza layer had all the background info on it. In this case the Canvas Size box to indicate extention color was grayed out.
If I just flatten or merge down to the Background, then all is well.