Full boil or partial? And did you do a late extract addition?
If you did a 2.5 gal boil with those hops for 60 minutes, and added all the extract at the beginning, you got about 12 IBUs. This would be about half of what you need, and wold give you a pretty sweet beer.
If you did a full boil or added the extract late, then this probably isn't the issue.