javascript error during transitions

[proclivity]

Hi! I am sort of new to Flash 8 and I've been doing this tutorial for my thesis thru it...while I was doing some transitions (not the manual transitions -- the one under timeline effects when you rightclick your mouse towards an object), this error always shows up that prevents me from implementing any transition at all.

Here's the pop-up error message :
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While executing <filename>, the following javascript error(s) occured:
A set with that name already exists.

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I am sort of confused because I never used any commands that would lead to a javascript error, I think.

Please help me clear this up. I would really appreciate any form of help

BTW, i tried making a new Flash document and the transitions work well..it's only in the document I've been working on that this error occurs.

Thanks so much.