At Prepare Windows PE Image dialog, clicked Next and it went through mounting and unmounting Windows Image File.  The message above the progress bar
is "Installation not complete"..  Clicking the Next button after this message appears just goes through the same process over again. I never see the media creation page.
There are errors in the log shown below:

Deployment Image Servicing and Management tool
Version: 10.0.10240.16384


Error: 1812

An error occurred while attempting to start the servicing process for the image located at c:\boot\macrium\WA10KFiles\mount.
For more information, review the log file.

The DISM log file can be found at C:\Windows\Logs\DISM\dism.log
Setting scratch space

Deployment Image Servicing and Management tool
Version: 10.0.10240.16384


Error: 1812

An error occurred while attempting to start the servicing process for the image located at c:\boot\macrium\WA10KFiles\mount.
For more information, review the log file.

The DISM log file can be found at C:\Windows\Logs\DISM\dism.log
Failed to load offline registry hive: An invalid name request was made. The name requested cannot be retrieved at this time.
Unmounting the Wim - 3/2/2016 3:16 PM
=====================================

Your problem appears similar to one that was the topic of an earlier forum thread posted here that was addressed by a Macrium rep who suggested a clean boot to isolate the cause.  Apparently the suggested clean boot solution worked for that user and so would be worth trying in your case as well.  Windows clean booting is explained in this Microsoft KB article.

Regards, Richard V. ("Arvy")

I did a clean reboot of Windows 7, and got the exact same errors recorded in the log and the exact same behavior of Macrium Reflect.  Any other ideas?

I posted some other errors I found in the log below:
Copying 'c:\boot\macrium\WA10KFiles\mount\windows\boot\efi\bootmgfw.efi' to 'c:\boot\macrium\WA10KFiles\media\bootmgfw.efi'
FAILED -2145452027
Copying 'c:\boot\macrium\WA10KFiles\mount\windows\boot\efi\bootmgfw.efi' to 'C:\ProgramData\Macrium\Reflect\Windows Kits\10\Assessment and Deployment Kit\Windows Preinstallation Environment\amd64\bootmgfw.efi'
FAILED -2145452027

Thanks.

Sorry, no I don't have any direct experience with that particular problem and I'd rather not offer you a bunch of wild guesses.  It looks like it might be a Reflect set-up problem and it couldn't hurt to try re-downloading and re-installing.  Apart from that, however, your best bet is probably to open a support request ticket with Macrium directly.

Regards, Richard V. ("Arvy")