TYPO3 Core

Hi there,
I upgraded a Typo3 websites from 4.1.7 to 4.2.1 and everything worked perfect. But after some time the first website hang up with the following error shown in the frontpage:

Fatal error: Cannot access protected property t3lib_pageSelect::$cache_getRootLine in /home/typo3_src-4.2.1/t3lib/class.t3lib_page.php on line 549

I tried to delete all caches (the typo3temp directory, the Typo3 cache and even cleaned up the database using menu 7 of the installation tool, but I couldn't solve the problem with this. I got another different but likewise error after deleting some caches:

Fatal error: Cannot access protected property t3lib_pageSelect::$cache_getPage in /home/typo3_src-4.2.1/t3lib/class.t3lib_page.php on line 192

The backend seems to work just fine, but the frontend just displays these errors (with error-reporting on in php.ini).

I decided to downgrad to Typo3 4.1.7 and this solved the problem - the page works again. But when I switch back to 4.2.1 the same error is displayed again. For that reason it seems to be a bug in Typo3 4.2.1 (?). Can somebody reproduce/confirm this error?

I am not sure, but may be the error was first triggered by a quota limit, so that no new file could be created - the quota of the website was nearly exceeded when i first saw this error. But when I increased the quota and cleared all caches the error was still there.

I found another user who seems to have the same problem posted in :

http://www.typo3.net/forum/list/list_post//80321/?page=1#pid302183

This is a german Typo3 forum.
(issue imported from #M9392)