[Zope] Zope hangs easily.

Hi, I am a newbie to Zope. I installed it on a Sun machine with Solaris 8. I used ./start & to get Zope running. However, it hangs easily. When some one downloads some pdf files, it will stop running. Also, I started the ftp server as well. However, whenever I connected to the ftp server, Zope will also stop running. Can any one tell me if I am missing some important steps? Thanks! I used Zope-2.6.0-solaris-2.8-sparc.tgz from www.zope.com. FYI, my server is running at neman.usc.edu:8080. FTP server is running at port 8021. Best regards, Jingzhao