[TYPO3-english] 6.1.8 => 6.2 Install Tool failure

[Tony Lush]

After preparing a 6.1.8 site for upgrade and switching the symlink to 
6.2.1 (and emptying the typo3temp directory), I got the request to 
create the ENABLE_INSTALL_TOOL file. After creating that I only get a 
white screen at .../typo3/sysext/install/Start/Install.php

In the typo3temp directory only an empty locks directory is created. No 
files are in that directory.

I had successfully made an upgrade from 6.1.8 => 6.2.1 elsewhere on the 
same server.

Error reporting is on, but none are displayed. I have fixed one issue 
with the extension VHS (https://github.com/FluidTYPO3/vhs/issues/506).

This particular site is based upon the Ecodev bootstrap_package, which 
uses flux, fluidpages, vhs, fluidcontent, and fluidcontent_bootstrap.

Has anyone any suggestions?

Thank you -- Tony