Well, if you brewed with WLP400, then it might be normal. This yeast seems to like to take his sweet time. It took 3 weeks for the kraeusen to fall in my batch, with a very healthy yeast. For other people, on the WLP400 review of whitelabs, it seems like a little swirling to resuspend the yeast was needed to have proper attenuation.
So, I guess we have to deal with the yeast's agenda.