It turns out your texmap was also the wrong dimensions - you had 8197x3074 and it should have been 8192x3072, but I can resize that one without trouble. (Heightmap is N*64+1, texmap is N*512, where N is X or Y, in your case X=16 and Y=6.)
The map now compiles and at first glance looks as you'd want it too, but it suffers from "terracing" - see attached. I remember this problem from olden times, and I think its caused by your png heightmap having insufficient bit depth to express what Spring views as a smooth change in height. I personally avoid this issue by using .raw heightmaps, but I do know that some people managed to fix their pngs.
Files, get it while its hot:
http://www100.zippyshare.com/v/2S0xPYXh/file.html