in both DIrector MX and DIrectot MX 2004.
in the Text library's Custom Scrollbar
line 358-362:

locAdjust = myMember.regPoint - [0, mySprite.height]
rectAdjust = mySprite.rect - rect (mySprite.loc, mySprite.loc)[h]
---??[/h]
mySprite.loc = point (scrollLeft, scrollFloor) + locAdjust
[h] -- myActiveZone = mySprite.rect ???[/h]
myActiveZone = rectAdjust + rect (mySprite.loc, mySprite.loc)

some confused codes!
the outcome: the scroll-text's down arrow can NOT auto locate its location!
to fix it, comment the confused-codes ,i use :

rectAdjust = mySprite.rect - rect (mySprite.loc, mySprite.loc)
---??
mySprite.loc = point (scrollLeft, scrollFloor) + locAdjust
myActiveZone = mySprite.rect
--???
myActiveZone = rectAdjust + rect (mySprite.loc, mySprite.loc)


it's Macromedia's error?