Midi out of sync in 1.6.4

[Erik Sandberg]

Hi,

When compiling the following score with 1.6.4, the two staves' midi tracks 
are not synchronised. The first staff finishes about 1/32 before the second 
one. This does not happen if the grace note is a c instead of a g.

\version "1.6.4"

\score {
  <
    \context Staff = I \notes { \grace g8 c16 c32 c c8 c c c c c c }
    \context Staff = II \notes { b8 b b b b b b b }
  >
  \midi {\tempo 4=90}
}

Erik