[TYPO3-install] Blank page after upgrading from 6.1.7 to 6.2

[Andrey Aksenov]

There are several sites running on TYPO3 6.1.x and 4.7.x 
After the upgrade (as usual, with symlinks in a new folder TYPO3 6.2, cleaning typo3temp). But then is redirected to http://mysite.com/typo3/sysext/install/Start/Install.php and blank page...
Output configuration errors is enabled:
'SYS' => array(
..
		'devIPmask' => '95.73.109.233,195.128.48.140,*',
		'displayErrors' => '2',
..
),

But it does not help. I repeat, on TYPO3 6.1 everything works fine.
In addition, on the same server running a website on the 6.2, but it originally was on this version of TYPO3.
After such a pompous presentation of the new TYPO3 version it was not as rosy.
Who can tell what may be a bug. How to include at least display errors that occur?