[CentOS] RPM conflicts - help!

I'm building a database/application server with a Dual-Opteron 64 bit system. 

I need to run PHP4, Apache, and Postgres 8.1, but I'm having conflicts with 
Postgres 8.1 and PHP 4 that comes with CentOS. 

History: 
1) I installed Apache and PHP with yum. 
2) I then installed PostgreSQL 8.1 RPMs from the PG website. 
3) Then, I tried to install php-pgsql with yum - and it didn't work, 
complaining about pgsql.so.3. So, I installed with --nodeps and symlinked the 
/usr/lib64/libpq.so.4 -> /usr/lib64/libpq.so.3. 

Now, PHP and PGSQL work without any problems. But now, I can't do a yum update 
- it still complains about pgsql.so.3! 

What can I do to resolve this? 

Thanks, 
-Ben 

-- 
"The best way to predict the future is to invent it."
- XEROX PARC slogan, circa 1978