lock screen doesn't!

[AbilityForms at aol.com]

Hi everyone,

I'm using Mac OSX. Why is it that when I use the following script I get a 
flash of stack "otherStack"? I thought lock screen wouldn't allow that to happen.

on mouseUp
    lock screen
    push cd
    go stack "OtherStack"
    pop cd
    unlock screen
end mouseUp

Joe,
Orlando, Florida