I would do it this way instead:
Code:
$("#myid").animate({opacity:'toggle'},'slow');
The slideToggle() method toggles the display from
hidden to
block and vice versa instead of (hidden / inline-row).
Tested:
Code:
$("#myid").css({display:'block'});
...the effect of having that code is the same as the problem you are experiencing.
Not sure for a real fix, but I would change to animate() method instead and play with opacity as it's stable.
Hope that makes sense.