Danny's observation concurs with our suspicion that this is most likely caused by some kind of caching. Restarting IIS does clear parts of the cache, and may help, but it does not clear all the possible places that can be cached.
I suggest that you follow the clear caching procedure. I suggest that you first follow the procedure for your development machine and that you include in that process both uppering of privateversion, as well as the deletion of both obj and bin folders of your project. When you build, those two folders will be recreated and it makes sure that the most recent versions of the Gizmox assemblies are copied. After that, go to your server and delete the bin folder your application's virtual folder. Then deploy your application, edit the server's web.config and upper the privateversion there.
It goes without mention that in case of disaster, please make sure you have proper backups of all the folders you are updating.
Please let us know if this works for you.