TYPO3 Core

When I upgraded from 4.1.5 to 4.2.5 with success. No errors and warnings. When I changed typo3 symlink and TYPO3_mainDir in four files mensioned in "Changing the default “typo3/” directory" the pages tree in middle column in BE doesnt expand.

FireBug says that in file http://mysite/typo3/ajax.php?ajaxID=SC_alt_db_navframe (...) error has occurred

<b>Warning</b>: t3lib_div::require_once(/home/tommy/public_html/typo3/alt_db_navframe.php) [<a href='t3lib-div
.require-once'>t3lib-div.require-once</a>]: failed to open stream: No such file or directory in <b>/home
/tommy/public_html/typo3_src-4.2.5/t3lib/class.t3lib_div.php</b> on line <b>4687</b><br />
<br />
<b>Fatal error</b>: t3lib_div::require_once() [<a href='function.require'>function.require</a>]: Failed
opening required '/home/tommy/public_html/typo3/alt_db_navframe.php' (include_path='.:/usr/lib/php:/usr
/local/lib/php') in <b>/home/tommy/public_html/typo3_src-4.2.5/t3lib/class.t3lib_div.php</b> on line
<b>4687</b><br />

There is no typo3 directory in my public_html and alt_db_navframe.php exists in my secret directory. So i suspect that somewhere typo3/ is hardcoded.

(issue imported from #M10458)