I like to design 950px wide since I like the extra space, and I know my target audience is people with broadband connections and widescreen monitors. But that's just me.

If you need 95-100% compatibility with screens, I would aim for a design that works well on 800x600. If you have an web statistics package (like Google Analytics) that reports on your target users' screen sizes, it makes the decision easier.

The reason your flash links don't work is probably because of MySpace's Flash restrictions, which turn off all clickable links.

More here:

http://mashable.com/2006/07/21/myspace-update-threatens-youtube-rockyou-and-hundreds-more/

Your best bet is to use HTML for your "Add as Friend" type links.