[TYPO3-english] Upgrade to 4.5 => Lock file create issue

[Tony Lush]

I upgraded a server to PHP 5.3.21 and MySQL 5.1.66. That allowed me to 
upgrade a number of sites to 4.5 and up. On one site, though, I am 
having an issue.

After upgrading through to 4.5, any frontend pages visited produce a 
'Lock file could not be created' error. When I switch back to 4.4, the 
error goes away.

The Install Tool reports that folders are writable, and I have confirmed 
that [BE][createGroup], [fileCreateMask] and [folderCreateMask] are set 
properly.

additional_reports also shows the directory as writable.

I have removed deprecated and unused extensions, and cleared the 
temp_CACHED... files after each action. The log file does not display 
any issues there. There are no more items in the deprecation log.

Googling has not been productive.

What else can I do to track this down?

Thank you -- Tony