Nagios 2.2 has just been released and can be obtained from:
This release fixes a segfault (introduced in 2.1) that could occur during flapping service notifications, so if you're using 2.1 its time to upgrade. Thanks to everyone who helped track down this problem.
Here's the changelog...
* Minor bug fix in availability CGI
* Bug fix with temporary file location used for retention data
* Fix for segfault that occurred in 2.1 during service flapping notifications