fishy guts:

My first guess would be the hair. If it is the fine stuff; it just doesn't flair as well. Look for patches of hair that appear and feel waxy and have even tips. The hair that works best for me has a diameter at the butt that is rather thick.

Second guess would be the amount of tension applied when wrapping the hair. If you can easily pull the fibers out it's too loose. Practice breaking your thread so you get an idea what the breaking point is and tighten down your wraps just below that point.

Hope this helps.