Internal error when saving png to network drive

This question has been asked before, but I have not found an answer.

When I try to save a Fireworks file as png to a network drive an internal error occurs.

I can save other file types to the network and I can save png to the desktop, but not png to network.

File size seems irrelevant.

Any idea what the problem is?

I use Fireworks CS6 for Windows.