You're using File > Import MIDI right?
If you are, there should be something called "Fruity LSD" that pops up. Make sure the port number is 0.
If it didn't, go to your mixer , and click on Insert 1. Then click on Fruity LSD to open the plugin.
In Fruity LSD, if the port number is not 0, switch it to 0. Try playing it again.
All I can think of at the moment.
Also, shouldn't FL8 auto-update to FL9?