It will not keep the uri that I type into the field in my entry. When I go back into the entry, it is back to the example/pages/uri. I have used module on this site in the past, I had uninstalled it and now re-installed it. Could this be a problem?
It's worth ensuring that the Pages module is properly installed (Addons > Modules | Status: Installed). Also, it's worth trying Addons > Modules > Run Module Updates in top right corner of the page.
Other than that ensure that the Pages module is configured correctly in Pages > Module Configuration. Ensure that you've set the default blog and template to use.