Same problem. I was sharing my PS3 and we used either of our accounts to watch Netflix. Now it is mine alone and I cannot log him out. He's not happy at his new house when he his queue is all changed after I use it.
I've seen this problem posted on forums all over the place. It should really be addressed.
1. Sign into your account on the Netflix website
2. Click on the "Your Account and Help" link in the upper right corner
3. Click on the "Manage Netflix ready devices and computers" about halfway on the page
4. Click "Deactivate" for the PS3 system
I guess actually the person who's account should not be on there needs to do this. You'll have to activate your PS3 for your account a similar way.
That didn't work. He deactivated it from his end several times and it would just reactivate. He finally called support and they told him a fix that I thought was a joke. It worked about the 4th time I tried. I had to do it quickly.
Go into the Instant Queue. Then on your controller (quickly) go
up up up up
It popped up a box for me to deactivate his acount.
Now it is going through the login process.