Firefox says users need to upgrade their version, but users already have the newest version?

Here is my problem: My department has multiple computers that users log into via roaming profiles and folder redirection. For some users when they log in, they are ALWAYS told that they are running some older version of firefox (usually 3.6.3 I think) and they need to upgrade. However, when I go to About Firefox they already have 3.6.16. It seems like their profile is somehow 'stuck' thinking they are using an old version. Does anyone know how to fix this without deleting their profiles? Does anyone know why this happens to some users and not others?

Thank you, Jennifer