Are you sure you have the latest Admin resource?
If you would like to get the latest resources you must download an SVN client from HERE
Then after installing right click on your desktop and you should see 'SVN checkout', click on that and then enter this link http://multitheftauto-resources.googlecode.com/svn/trunk/.
Now, to save you from reporting another problem that;s going to pop up I shall tell you what to do, once you manage to get the latest resources, after pressing P the Administrator panel shall come up but you wont be able to click on anything, so open that file of the Administrator resource and click on 'conf', you shall see a acl.xml, now open it and migrate all those functions to your main acl.xml and you should be done.