system() has been disabled for security reasons

Hi,
My hosting provider have disabled the following modules and my site admin panel no longer works:
exec
passthru
shell_exec
system
proc_open
popen
show_source

The error I get is as follows, when trying to login to http://mysitename.com/wp-admin :
Warning: system() has been disabled for security reasons in /home/username/public_html/wp-includes/cron.php on line 244

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-includes/pluggable.php on line 868

And similarly (although I do actually see the login box), if I try login by going to http://mysitename.com/wp-login.php:
Warning: system() has been disabled for security reasons in /home/username/public_html/wp-includes/cron.php on line 244

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-login.php on line 302

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-login.php on line 314

…if I do try login I still get a similar, but slightly different error:

Warning: system() has been disabled for security reasons in /home/username/public_html/wp-includes/cron.php on line 244

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-login.php on line 302

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-login.php on line 314

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-includes/pluggable.php on line 665

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-includes/pluggable.php on line 666

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-includes/pluggable.php on line 667

Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-includes/cron.php:244) in /home/username/public_html/wp-includes/pluggable.php on line 868

I’m using WordPress 2.9.x (not sure what the minor version number is).

Is there any way around this problem?

thanks,
Baronne