Remember that using out-dated software or plugins can be a security issue.
For example, in the release notes for Greasemonkey 2.0 (the one you guys are downgrading from), it says:
"For stability, reliability, and security the privileged sandbox has been updated to match the new changes to unsafeWindow for the Add-on SDK."
Looking at the rest of the release notes, this is specifically why the FSH isn't working with GM 2.0 ("these changes will break some scripts. These scripts will need to be updated to work correctly again.").