I am using version 2.6.8f and when I create or edit a custom field, the page that opens breaks out of the Joomla admin template and there are no "Save" controls on top of the page. So I can't save any of the changes or create new entries.
This is a php issue. You need php 5.2 or later. Contact your host and have them upgrade php on your account. This should not be a big deal at all. If it is... then you should reconsider who is hosting your site Once this is updated, you'll find the issue to be resolved. Thanks.