I haven't had time to really look into it.  As a work around in the mean time.  You can run a simple bat file with this command "TZUTIL /s “Pacific Standard Time” adjusting accordingly for your timezone."  

All I know is that the issue is coming from the default unattended file, because I didn't have these issues when i used a custom made one.

I tried this, but it doesn't seem to work 100% of the time. How are you running tzutil? I was attempting to run it as a through a script job after the imaging process is complete.

 I created a .bat file.  That contains only tzutil /s "Central Standard Time".  Than I push it out as the last task in my imaging job.

Have you tried modifying the xml file using the Windows Automation Installtion Kit?  I don't use the altiris unattend.xml file for my install because we wanted to do more with our image automatically so we generated one with the WAIK or really the WSIM which is the actual tool used to create/modify the unattend.xml file used for automating the installation of windows 7.  It is a free tool and very easy to use (once you get used to it).

I was able to get it working:

I unchecked "Automatically perform configuration task after completing imaging task" for the image.

I then run a script to change the time zone.

After that I run a config job to add the system to the domain.

Spazzren:

I've looked at WAIK, but I think it's probably overly complex for our needs. I try to keep our build process as simple as possible as a general rule. What types of tasks do you perform that require the manually creating the xml file?

We don't do much with it, and once you have one that will work for you, you really don't need to mess with it again, and it make the build process much more simple for us.  Ours pretty much just sets the computer name, the product key, registered organization and owner, timezone, The local languages and input, hiding of the eula, and the administrator password.  Basically only what is needed to get the computer to boot directly into Windows without any prompts by the setup. 
It does look very complex at first, but you do not need to use everything.  The unattended.xml file you are using can just be modified with WAIK (WSIM) to get it work with the correct timezone.  I am guessing that is where it is setting the wrong timezone.  In case you start looking into it, the timezone is set in the Microsoft-Windows-Shell_Setup_Neutral in the oobeSystem section (add it to the oobeSystem setting to get it to work correctly).