After upgrading to Typo3 4.2.0 I ran into a annoying bug. Typo3 raises a javascript popup if your backend login has expired. But my Typo3 raised the popup every time i saved a page and asked me to login again ! But fortunately this is a known bug and the patch works fine.
http://bugs.typo3.org/view.php?id=8336
I ask myself when will the patch the ugly typoscript to make it understandable and readable 