[f9][AS2] rollOver twitch that I can't see

Greetings all,
I have made a little eCard game for the company I work for. The CEO is reporting an issue with it that I can't see on any other machine.
Here's a link to the eCard:

http://sledex.centresource.com/

The problem is:
After clicking the Play button, there will be a few tabs at the bottom left. When you click them they should pop up a bit - if you click on them again they should:
"Need an eCard" = opens a new window of the company's website
"Send To A Friend" = pops out a mailTo form
"High Score List" = pops out a High Score Table

He's saying that when he rolls over them they twitch & flutter between popped out & put away. If he clicks they go away (when he's able to click) - he's not able to interact with them in any intended way. He's not able to click to open the websites window, he's not able to open the Send Friend form, & he's not able to view the High Score list. I've tested this on several other computers (both Mac & PC) & am not able to reproduce it. There's also NOTHING in the code that would cause a conflict (I've made sure several times). I attempt to explain that it's got to be something with his computer but he will not accept that.
So, my question is - Does anyone else have any issues with this?
Just go to the page, click Play, then mess around with the tabs in the bottom left (green one, red one, blue one) & see if you encounter any problems, or if they don't seem to be doing anything, or if they twitch.

Thank you in advance! :)

In a moment of haste, I had to remove the animation, & just go with a standard, boring, blase little click...
but he's happy that it works.
(though it wasn't broken before ;) )

Thanks, anyways :)