Pop-Up problems!

A client of mine has been having A LOT of problems with the window pop-up script that I got from this Kirupa tutorial: http://www.kirupa.com/developer/flash5/newwindow.htm

This is the most basic pop-up I think that I would use for flash. Actually I believe that it uses javascript in the HTML document. For some reason though, it isn’t working on all systems. Since it is a client that paid for it, they are not going to shut up until it works on EVERY system, or any that anyone they know will use.

Anyone know what the deal is or if anyone has got a better script? Please help since this is URGENT!