Grace notes are not playing properly.

The acciaccatura plays 1/8 of the note previous to it.
ex: If the note previous is a quarter note, the grace note plays like a 32nd note. If the note previous is a double-whole note the grace note plays like a quarter note

The appoggiatura plays equivalent to an eighth note except for when the previous note is less than or equal to an eighth note. In that case it still plays as an eighth note before it as a separate voice.

The rest do not play, even when the previous note is a longa.

I always input them in by either clicking and dragging them from the palette or selecting the note(s) first and double-click the grace note I want. I have seen this problem on all pieces using them on musescore.com and on all downloaded pieces from that web site, and I have heard a complaint from another person who has posted many pieces on MuseScore.com

Operating system: Windows 7
Version of MuseScore: 1.0