also click the check box that lets you run flmm in xp compatability mode.
Rightclick the flmm icon, click properties then compatability, click the check boxes for run as admin and run in compatability mode and you should be ok. I'm running the same os and did that and have had no problems. i also did the same with fl itself.
the only thing that won't work is account mamanger but you can work around that by using multiple accounts on your pc and switching between them. you will need to enter your fl multiplayer ac no. when you start up the game fro the first time in these new accounts but after that your away.
By using this method you can also have multiple chars on the server at the same time, don't know why you would want to but you can.