apache exit signals

I have rented a new server and installed freebsd 6.1 on it, with
Apache/2.2.3 (FreeBSD) DAV/2 PHP/5.1.5 mod_ssl/2.2.3 OpenSSL/0.9.8b

But I get a lot of exit signals in my httpd-log - both Abort trap (6)
and Illegal instruction (4).

I really can't find out if it is freebsd, apache or php that causes the
problems. The webpages that causes the exit signals worked fine on my
old server (freebsd 5.3, apache 1.3 and php 5).

It seems to be pages that requires a certain amount of computing that
result in the exit signals.

A few lines from the log:
[Tue Aug 29 07:45:27 2006] [notice] child pid 14013 exit signal Abort
trap (6)
[Tue Aug 29 07:45:28 2006] [notice] child pid 14211 exit signal Abort
trap (6)
[Tue Aug 29 07:48:27 2006] [notice] child pid 14118 exit signal Illegal
instruction (4)

Any ideas where to look?
Regards,
Jeppe