Asterisk 1.8.3 crash AGI

I have a problem with Asterisk 1.8.3 AGI PHP.
There is a very low load of calls, but occasionally the Asterisk crash for no reason. in a log file there is nothing. Asterisk not have time to write anything.

in messages

CentOS 5.5 kernel 2.6.18-194.32.1.el5 x86_64 Asterisk 1.8.3 dahdi 2.4.1 PHP 5.1.6

Please help !!! … +Backtrace