I've installed zend server CE for php 5.3 and it seems that yum dependencies have been broken. You should see this.

[root@icedbox Downloads]# yum update
Fatal Python error: pycurl: libcurl link-time version is older than compile-time version
Abandon (core dumped)

Don't panic, take a deep breath. Here is how to fix the problem.

1) Download via ftp libcurl

ftp://fr2.rpmfind.net/linux/fedora/updates/14/x86_64/libcurl-7.21.0-6.fc14.i686.rpm

2) Install libcurl

rpm -Uvh --force libcurl-7.21.0-6.fc14.i686.rpm

3) Edit /etc/ld.so.conf.d/zend_server.conf
add /usr/lib at the beginning of the file

ldconfig

Enjoy.