Michael,
  My bus has the same problem -- I've found that by pushing down (as if to
  get round the reverse lockout), I can move straight into first.  This
  makes me think that it's a linkage problem and not a box problem -- I've
  adjusted the linkage plate at the base of the shift lever a bit
  (remember to mark the original position w/grease pencil first) and this
  weekend I'm going to have a go at the linkage under the bus.  A couple
  of volks on the list also recommend replacing the plastic bits at the
  shift lever end of the linkage.  If you really want to isolate the problem, you can disconnect the
  linkage from the tranny, and with the bus up on jackstands, shift the
  box directly via the shaft coming out of the tranny which mates to the
  linkage.
Best,
d.
1990 GL "Mudskipper"