The fade in/out effect used for the title screen, between levels, etc, can
be very slow when running on an X server display other than local. The rest
of the game seems fine though.
The fading method could do with being modified (or removed?) when running
over a non-local connection (something is certainly needed over 10Mbit
Ethernet) and/or with a lower-performance X server.
This isn't really a bug. And to honest most users (although you're the exception
to the rule) won't run games over the network like this.