TYPO3 Core

I've developed a tca-based database application without BE modules for TYPO3 4.4.

Now I had to update the system to TYPO3 4.6

In the extension, there are configured backend-tabs (set in ext_table.php):

$TCA['table']['ctrl']['dividers2tabs'] = '1';

The 'showitem' array in tca.php is set correctly, and all works fine with TYPO3 4.4.

When I'll create a new record, switch to text and create a new inline-record (with MM relation) and switch the tab again, it's not working.
The tab action succeeds, but the text-tab is still visible. The requested tab is in front or next to the last tab-view.
Please look at the screenshots to understand.

I hope you understand, what i mean :-)
thanks in advance

Patrick