inconsistent spacing between piano staves

[jim cline]

I managed to use lilypond to typeset a choral piece with decent results,
but I am now working on my first piano piece, and encountering a strange
problem.  The first system has much more space (ridiculously too much) between 
the treble and bass staves than the second system.  It is an extension of the 
simple template for piano music provided by the lilypond documentation.  I 
tried commenting out the two vertical spacing specifications to see what 
effect that might have, but the problem remains.  (I would like to include the
.ly file below, but this interface will not allow me to do so, as it thinks
I am "top-posting".)