Sorry; keep getting called away from my further response....
There are a number of causes of this problem and several fixes and/or workarounds. Some of these problems may result in an "encode failed" error or the photoshop -1 error.
Long filenames: an asset filename (without the extension) of greater than 79 characters (including spaces) will fail.
Long paths may also cause issues; I have not tested them.
Special characters being included in filenames, including @, /, \, etc. Use only alphanumeric, and use underscore for separation.
Special issues in Photoshop, resolved by, for example, flattening some special layers.
