When I ran this on a Mac, it didn't do what I expected... I also found out that there's a visual effect "slide", which is currently undocumented. However, there isn't a "slide down" or "slide up", just a "slide". But I found that I could get the best effect using this:
on mouseUp if the vis of group "grpSlide" is false then show group "grpSlide" with visual effect slide else hide group "grpSlide" with visual effect reveal up end if end mouseUp
on mouseUp
if the vis of group "grpSlide" is false then
show group "grpSlide" with visual effect slide
else
hide group "grpSlide" with visual effect reveal up
end if
end mouseUp