Normal note duration too short when tied to grace note

using R2887 on Windows XP.
Create a blank piano score.
Create a few notes in the bass clef, then with one of them selected, double click the note with slash on the pallet to enter a grace note of the same pitch.
repeat for the rest of the notes.
In edit mode, then, tie each grace note to its main note.
Enter a few notes in the treble clef alligning with those in the bass clef.
Rewind and play.

Expected:
The notes in the bass would sound slightly before the notes in the treble, and sustain until the next bass note.
Resulted:
The notes in the bass do sound slightly before the treble notes, but they sound staccato.