\version "2.15.40"

first =  \relative c' {
  b8( c)
  % uncomment and the hammer-on "bug" goes away
  b16 c cis d
}

second = \relative c {
  d8( e)
  %d16 dis e f
}

\score {
  \new StaffGroup <<
    \new Staff = "staff" <<
      \context Voice = "first voice" { \clef "G_8"  \voiceOne \first }
      \context Voice = "second voice" { \clef "G_8" \voiceTwo  \second }
    >>
    \new TabStaff = "tab" <<
      \context TabVoice = "tab first voice" { \clef "moderntab" \voiceOne \first }
      \context TabVoice = "tab second voice" { \clef "moderntab" \voiceTwo \second }
    >>
  >>
}