Precise Steps:
0. Login as admin 
1. Install Chrome from http://pack.google.com (to get a system level install of chrome)
   1.1. Login to a non-admin account and make sure that you can access Chrome
2. Download the channel changer and switch to beta
3. Go to wrench > about google chrome to update to 2.0.172.6

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This is a showstopper. We have a significant population with system level installs now 
(via Pack and other partners). 

If updates are breaking Chrome for non-admin users (or users with UAC on), we need to 
fix this right away.

Is it possible that the issue is with Omaha? Don't they handle elevation for the Google 
Chrome installer on Vista?

I don't know the exact details of this but I was under the impression that user level 
install was not allowed when you had a system level install already.  Having the 
installer fail gracefully in this case would be the right way to go?

This happens on XP as well. System level Chrome is not accessible by NonAdmin user when 
you update from 154.53 to 172.6. 

Sunand, Please try with Chrome installers to see if this is Chrome issue or omaha 
issue.

Now I know the problem. This has nothing to do with update. System level installs are 
just broken. You can do a clean install of 172.6 with --system-level option and non-
admin user will not be able to start Chrome.

We recently started moving Chrome files instead of copying them and the moved files 
take default permission of being accessible to only current user.

 Issue 9339  has been merged into this issue.

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The following revision refers to this bug:
    http://src.chromium.org/viewvc/chrome?view=rev&revision=13979 

------------------------------------------------------------------------
r13979 | kuchhal@chromium.org | 2009-04-17 16:23:54 -0700 (Fri, 17 Apr 2009) | 6 lines
Changed paths:
   M http://src.chromium.org/viewvc/chrome/trunk/src/chrome/installer/setup/install.cc?r1=13979&r2=13978

In system level install case go back to copying files instead of moving them.

BUG=10656

Review URL: http://codereview.chromium.org/79060

------------------------------------------------------------------------

(No comment was entered for this change.)

The following revision refers to this bug:
    http://src.chromium.org/viewvc/chrome?view=rev&revision=14014 

------------------------------------------------------------------------
r14014 | mal@chromium.org | 2009-04-18 20:36:57 -0700 (Sat, 18 Apr 2009) | 7 lines
Changed paths:
   M http://src.chromium.org/viewvc/chrome/branches/172/src/chrome/installer/setup/install.cc?r1=14014&r2=14013

Merge r13979

In system level install case go back to copying files instead of moving them.

BUG=10656
TBR= kuchhal@chromium.org
Review URL: http://codereview.chromium.org/79084
------------------------------------------------------------------------

Works fine with Google Chrome 2.0.172.8 (Official Build 14017)

Works fine with Google Chrome 2.0.172.9 (Official Build ) as well

Works fine with Google Chrome 2.0.172.22 (Official Build )

Am having similar experience w/ UAC & failure of Chrome to work when Chrome passes a 
silent update.  Actually caused me to uninstall Chrome, but I came back.  Suspect 
that issue is a combination of UAC & antivirus program.

Running Vista Home Premium, fully updated.
Using Norton Protection Center / Norton Security Online.
Chrome installed as individual software (not via pack)

When using account as a standard user, Chrome works fine until Google issues update.  
As a standard user w/ UAC activated, will arrive at a "page cannot be displayed" type 
message.  No indication as to why this won't work or source of error

However, if I change my account to Admin, restart, and then try to launch Chrome, my 
antivirus program will pop up a window saying that Chrome.exe has been changed (and 
then the option to always allow, block, etc.).

If I click always allow, Chrome starts working again.  However, if I then change my 
account back to standard user, I run into the same problem when a silent update comes 
along.

Bottom line is that norton antivirus doesn't launch a window stating that chrome.exe 
has been changed and just goes with the default which prevents Chrome from loading 
page.

I hate switching b/t admin and standard user.  Want to keep Chrome in play, but need 
ability to keep using after Google sends an update without changing my account to 
admin and jumping through all of those hoops.

corbinpmiller: The issue you are seeing is different from this issue. Looks like this 
has something to do with Norton. Please file a separate issue with more information of 
you system and anti-virus specs.

Thanks.