Program execution stops at exec()

Hello

In one script I use exec() to execute a shell script which takes 2-3
hours to run. I disabled user abort and set time limit to more than one
day. The shell script finishes well but no instruction after exec() is
run. The script finishes with no error nor warnings.
Some of you know hwat happens?
Thanx in advance.

Tom

Code snaps:


ignore_user_abort(1);

set_time_limit(100000);

(...)

exec('/home/tom/build.sh  >ouput 2>errlog');    //takes 3 hours to complete

//  *** Nothing from here gets executed, 'build.sh' script completed with 
succes ***

(...)

I'm using php 4.0.4pl1(can't upgrade) with Apache 1.3.19 on Mandrake