TYPO3 Core

Common habit is to cancel screen by hitting X in upper right corner.
If second user does so doing frontend editing to some content using rtehtmlarea the announcement that he/she has started editing stays for ever (until he/she has logged out from the same content some how; hard to find this method)

This effectively prohibits simultaneus content editing.

Typo3 4.0.5
PHP 5.1.6
MySQL 2.0.59
Linux/CentOS 4.4 (updated per at moment)
Browsers: Firefox 2.0.x and Opera 9.10 and IE 6/7

(issue imported from #M5130)