Apache Error on RHEL 4 undefined symbol apr_table_compress

On a fresh install of RHEL 4 Apache was working fine. All conf files
were untouched.

After running up2date, Apache stopped working.

In the error_log file there is an entry:

/usr/sbin/httpd: symbol lookup error: /usr/sbin/httpd: undefined
symbol: apr_table_compress

For each attempted access from a browser.

Interestingly I can access the httpd server using telnet such as

telnet $ip_number 80
GET /

and this works.

All configuration files are default. Any ideas?