back trace:

running a backup on a course (actually just clicking next on step 1 of course backup) is resulting in a child process segfault for me in apache ( php5.3.2-1ubuntu4.7 freetds+mssql) while exporting the course to test PULL-369 .. a similar issue's solution to disable gc isn't working for me either http://bugs.php.net/bug.php?id=51091

[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] not yet decoded, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] decoded, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP Notice: unserialize(): Error at offset 24188 of 24192 bytes in /home/aparup/mcode/m20/mssql/moodle/backup/util/dbops/backup_controller_dbops.class.php on line 83, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP Stack trace:, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 1.

{main}() /home/aparup/mcode/m20/mssql/moodle/backup/backup.php:0, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 2. backup_ui::load_controller() /home/aparup/mcode/m20/mssql/moodle/backup/backup.php:81, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 3. backup_controller::load_controller() /home/aparup/mcode/m20/mssql/moodle/backup/util/ui/backup_ui.class.php:125, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 4. backup_controller_dbops::load_controller() /home/aparup/mcode/m20/mssql/moodle/backup/controller/backup_controller.class.php:315, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 5. unserialize() /home/aparup/mcode/m20/mssql/moodle/backup/util/dbops/backup_controller_dbops.class.php:83, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] unserialized, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP Fatal error: Call to a member function is_checksum_correct() on a non-object in /home/aparup/mcode/m20/mssql/moodle/backup/util/dbops/backup_controller_dbops.class.php on line 86, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP Stack trace:, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 1. {main}

() /home/aparup/mcode/m20/mssql/moodle/backup/backup.php:0, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 2. backup_ui::load_controller() /home/aparup/mcode/m20/mssql/moodle/backup/backup.php:81, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 3. backup_controller::load_controller() /home/aparup/mcode/m20/mssql/moodle/backup/util/ui/backup_ui.class.php:125, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [error] [client 192.168.100.27] PHP 4. backup_controller_dbops::load_controller() /home/aparup/mcode/m20/mssql/moodle/backup/controller/backup_controller.class.php:315, referer: http://aparup.moodle.local/m20/mssql/moodle/backup/backup.php?id=2
[Tue Mar 08 17:00:49 2011] [notice] child pid 22828 exit signal Segmentation fault (11), possible coredump in /tmp

i'm attaching the base64 in a file here just for reference.
Eloy has a test file that i'm attaching here too. (from PULL-369)