Install problem because "install file is damaged"

My client is periodically getting the following error on some of their identically configured Win7 machines:

"Sorry, an error has occurred.  The application could not be installed because the installer file is damaged.  Try obtaining a new installer file from the application author."

I am the application author.

Here is the install log from a problematic machine:

[2013-01-03:09:50:33] Application Installer begin with version 3.5.0.880 on Windows 7 x86

[2013-01-03:09:50:33] Commandline is: C:\Rate_Calculator\XXX_Air_Files\calc-xxx-rate_0_6_2.air

[2013-01-03:09:50:33] Installed runtime (3.5.0.880) located at c:\Program Files\Common Files\Adobe AIR

[2013-01-03:09:50:34] Unpackaging file:///C:/Rate_Calculator/XXX_Air_Files/calc-xxx-rate_0_6_2.air to C:\Users\xxxxxx\AppData\Local\Temp\fla3A80.tmp

[2013-01-03:09:50:34] Application signature verified

[2013-01-03:09:50:34] Unpackaging/validation complete

[2013-01-03:09:50:34] No app located for appID 'com.tappsolutions.calc-xxx-rate' and pubID ''

[2013-01-03:09:50:36] Converting unpackaged application to a native installation package in C:\Users\xxxxxx\AppData\Local\Temp\fla452B.tmp

[2013-01-03:09:50:37] Native installation package creation failed: [ErrorEvent type="error" bubbles=false cancelable=false eventPhase=2 text="Unhandled exception Error: open[110]: MSI Error" errorID=0]

Here is what I have done:

1) I searched the fourm and found this report with no solution: http://forums.adobe.com/thread/801670

2) I had the client send back the install file and I did a compare with an install file that was successfully installed on my machine; They are identical.

3) The client can specify a different install location to successfully install.

4) Client confirms that they did not install previous installs under a different user or administrator.

5) This problem does not happen on all machines; we do not know what the difference is between the problematic machines and non-problematic machines.

6) The problem began when I delivered 0.6.2 of my app, on the problematic machines they can go back to 0.6.1 and successfully install.

7) I unjared the 0.6.1 and 0.6.2 .air files and compared them.  Nothing unusual was found.

😎 The problem went away when I delivered 0.6.3, but reappeared when I delivered 0.6.9.