Hello together!

I have a very interesting problem on my webserver, a Suse Linux 9.1
with Apache 2.0.49:
After running a few hours the memory usage of the httpd2-prefork slows
down the whole system, not only web-sites.
when I put a ps aux | grep apache I get:
root 3777 0.0 2.3 61620 11364 ? Ss 10:59 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 3854 0.0 2.5 61956 12136 ? S 10:59 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 4975 0.0 2.5 62288 12508 ? S 12:02 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 5125 0.0 2.5 61964 12156 ? S 13:17 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 5127 0.0 2.6 62356 12588 ? S 13:17 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 5136 0.0 2.5 62108 12228 ? S 13:25 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 5254 0.0 2.4 61884 12060 ? S 14:09 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 5448 0.0 4.4 71264 21440 ? S 15:25 0:01
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 5459 0.0 2.3 61752 11488 ? S 15:29 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 5460 0.0 2.4 61860 12048 ? S 15:29 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf
wwwrun 5461 0.0 2.4 61752 11632 ? S 15:29 0:00
/usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf

You see that there are very many processes, getting more. When I kill
all except for one the system is nearly idle, but web-sites don´t open
fully and open extremely slow.

Does anybody know what this could be???

thanks,
petra