Time Zone keeps changing

I am just getting started using my new macbook (using OSX 10.5.5), and I can't keep the time zone from slipping back to GMT, so my e-mail and calendar events are listed as 5 hours later than they should be. I go into the time zone menu and change it to EST. It shows up on the map as EST, but when I close the window it resets itself to GMT, regardless of whether I've locked it or not. Help! I've searched the Help menu, but can't find anything useful. Thanks!

System Prefs > first tab > date & time > did you tick set date & time automatically? then set the closest time.apple.com. probably Europe.
The next tab ~ set the closest city in your time zone.
Restart your Mac to check that the setting stay. If not please come back.

I am having the same issue. I tried what was recommended and it is still slipping back to GMT. The time itself stays to what I set it but the time zone slips back. I do not set automatically to apple time. any other suggestions??

Thanks

Did you click the lock to prevent any changes?

ya forgot t include that...i think the lock is broken! The time zone changes even with it locked.