Comment 7 for bug 164709

This bug also occurs for filenames that actually have "%20" strings instead of spaces.

So attempting to open either "some file.xxx" or "some%20file.xxx" by double-clicking in Nautilus results in the error message: "failed to open file:///some%20file.xxx."

I wonder if this is a Nautilus issue, because the following commands issued from a terminal work just fine:
$ gmplayer some\ file.xxx
$ gmplayer some%20file.xxx