coredump during installation of iAS 6 SP4 on Solaris 2.6

We have iAS 6 sp4 and iWS 6 sp1 on Solaris 2.6 (updated patches!). We can install iWS, ldap, admin server, but if we install iAS itself we get a coredump right after enter the ports etc, before he starts to extract the data:

Finished with gathering of information.

Next, the iPlanet Application Server files will be extracted. After that,the iAS configuration and registration based on your responses will begin.

Press ENTER to continue: ./invoke_nas_preinst[15]: 7120 Segmentation Fault

ERROR. Failure installing iPlanet Application Server Main. Do you want to continue [n]?

[613 byte] By [709158] at [2007-11-25 4:51:19]