Basically the process is this:
When you first visit your profile/preference page a hash is created and saved to the database. That hash is put into a hidden variable on your profile/preference forms. When you submit, it checks to make sure that the hash from the form matches what was stored in the database.
If you're getting that error, then for some reason it's not matching.
Any script/template modifications added? Do you have any script/template modifications concerning those pages? Is it happening to everyone or just some?
