Problem solved , there were both layers and frames in the layers palette , same number of each when I loaded a gif from another source , or due to my following some option I thought I should do , like Flatten Frames into Layers. When I deleted all the Layers in the Layer Palette and just left the Frames there , it works fine. I think there are other problems with importing gifs from other apps though , , maybe I'd be better off just working from scratch in Photoshop.
Thanks to Nancy O for responding