It's looking very good, clearly laid out and professional. However I think you need to tweak a few bits!

Firstly, when the site loads, the logo animates in and then it cuts straight to your layout. Some animation of the logo moving and the layout appearing smoothly would be a better way to go as long as you can accomplish this quickly and with a little style. Not only would this use flash in a nice way, but animations can guide the eye around the page, highlighting your name and slogan as well.

Secondly, the text at the very top looks just the same as your navigation. I suggest you make it look more like your company name and tagline instead and better still, move your navigation up there too, underneath it! People are used to having the navigation at the top.

Thirdly, the text. As Smokie said, the text is blurry. Flash has a problem with text - It uses anialising which blurs the text and can make a great design look terrible. You can get pixel fonts (a google search will yield some results) which, if set at absolute points in flash (whole integers) will look very crisp and clean, especially if you switch to low quality. Considering you aren't using any shapes created in flash, you could safely go to "low quality" and not lose out at all visually. Experiment and see what you think - If you get confused on this then ask me as I have some experience with Pixel fonts!

Fourthly - Your music. Music is not a bad thing, but you have left the visitor no way of turning the music off. The only way they have is to leave your site. That's bad. You also preload the music BEFORE the site loads. That's bad too. Instead, wait until the site is loaded and the user can browse and THEN load your music and play it when it is ready. It's a bit of extra coding but it gets your visitors to the site faster! I also noticed that the broadband version has audio, the lower doesn't. You could include it in both and make your entrance easier, just by doing what I've suggested. You would only need one entrance button! (your current ones are too small too!). Also, you say you are loading the same amount of data on both, which clearly isn't true.

Your back button, that appears when you visit a section - Do you need it? I think you should keep the navigation on screen at all times. Visitors shouldn't have to click more than they have to.
Also, you're using a pop-up window. Some people just don't like them. Many have pop-up blockers. You're not using much screen space so I suggest you integrate it into a standard page. You can put a box, sides, etc around it. I did this with my page (it used to load in a window) which you can see if you like.

You've got a nice looking logo (how did you do that? I'd like to know!) and a well laid out and well presented site which makes good use of flash and actionscript. If you can improve it just a little by doing what I've suggested then it'll be more accessable and look a little better too.