outlook is reverting back to old http connection settings after outlook is closed??

my problem is that we have 2-3 users that when i change the http connection settings in outlook from e.g: origanal.servername.com.au to our new server name that was set up about 2 months ago to mail2.newserver.com.au and apply these settings they are applied and everything works great. when the user closes outlook then re-opens, outlook freezes and wont start up at all. i close out look from task manager and go into control panel\ mail then check the settings and the http connection settings have changed back to the old server name. i have removed the users profile on one of the machines and reconfigured from scratch but it still occurs. as the old exchange server was only recently removed as in about a week ago i have afeeling it may be a setting in exchange that i need to configure\change to stop this but i have had a look and cant seem to find anything that might cause it.. or would it be anything else on the machine?