when you start a new font, name it nicely, save it nicely, design in it nicely, but have never closed and reopened it yet (this is the important part): you might nearly always run into the following:
if you copy a layer in the layers palette, it will be named »(Null) Mar 20 15:20« (whatever). Until you closed and reopened the file, this will happen. Once you closed and reopened the same file it will start the correct behaviour, naming it (at least) »Regular Mar 20 15:20 (whatever your master is of course).
This is very messy and needs cleaning up effort. I guess this is a bug?!