I'm having the same problem as, except the 1.6 update you released is not fixing it for me on one website. I maintain separate live and development sites. I do not have this problem on my live site, but on one of the development sites I am seeing the error pop up. The only difference is that this particular development site is running PHP 5.3.2, while the live and other development sites are running 5.2.9.
I hadn't seen this problem until I started testing our PHP 5.3 compatibility.