your previous installation shouldn't be an issue.
I'm guessing that you created your database through goodies>mysql ? Or are you re-using the database from your previous install? You should start off your new installation with a nice blank database. You can just use the features in the one click install area to create a new datbase for you.
check out what I wrote in this thread about the third post or so down I out line instructions you should follow to create a new forum install. Hopefully that will help?