Hmmm, not sure what else it might be to be honest. I only use 32bit, so i can't even do a straight compare. It is odd that it works for some, and not others. Can you check the user permission groups (Menu>Administration>Users and groups) and compare the groups that the users are members of, and compare them to yours, see what is different? I've never had any problem like you describe, so I'm a bit puzzled as to what to suggest, as I've never had to troubleshoot the issue myself. Let me know if you find any differences. Hopefully someone else using the 64bit version may see this and have an idea I do not.
If you accept - and I do - that freedom of speech is important, then you are going to have to defend the indefensible. That means you are going to be defending the right of people to read, or to write, or to say, what you don't say or like or want said.