because I am sure it came because of php upgrade.
Me too, but I didn't find any reference anywhere to this segfault related with our php 5.2.1 and suPHP 0.6.2 :-(
Hans had a similar problem last April and with Falko and Till help arrived to the same conclusion: Disable suPHP on the affected sites.
(Posted to let others find a temporally solution)
Certainly it all doesn't looks promising.