(Sorry-- I had this posted in ActionScript as well -- not really an AS issue...)
I thought it would be easier for folks if they didn't have to create this from
scratch:
Here is the http://in.motion.com/flashSample/combobox_blues.swf
and the http://in.motion.com/flashSample/combobox_blues.fla.zip
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Greetings --
I traced back a bug that I was having to its most basic level and was
surprised that it happens with only a ComboBox component and a button symbol...
I traced it back so far that it got rid of all of my ActionScript and was left
with only these two interface elements:

Set-up: Create a new Flash document, ActionScript 2 / Flash 8. Drag in a
combobox component and add a label. Create a new button symbol and define up,
over, down and hit states and drag this in as well...

When you try test this movie, you get strange behavior... Give the button a
few clicks to see that it is working properly. Then, click on the combobox to
open it and then go back to the button. The button will work the first time
tried, but will not work properly with subsequent attempts. It seems that the
states of the button are getting confused after the combobox is used? (!?)

Could there be a work-around to this? Thank you in advance for you assistance
with this issue...!