[horde] mysql version 4+

[zebee at mighty.com.au]

I have a (well.. had a) working horde/imp setup,  on RH 7.2 using
homerolled apache (v 1.3.26) and  mysql (v 3.23.47) rpms.

The horde stuff is: 
horde-2.1-3
php-4.1.2-0horde1
php-imap-4.1.2-0horde1
php-mysql-4.1.2-0horde1

imp-3.1-2

I upgraded my mysql version to 4.0.10gamma as we need something it has.

Now, I get an error on implogin:

DB Error: extension not found

[line 102 of /data/web/mightymedia/public_html/horde/lib/Prefs/sql.php]

Naturally I worry it's the mysql upgrade.

Googling implies the problem might be in /usr/lib/mysql specifically
the mysqlclient version which is now 12 rather than 10.

What do I need to do to get horde working with the new mysql version?

What do I need to do to get webmail working again?  Do I need to compile
php? (I tried, and it fails at -lcrypto as the RH libs apparently require
kerboros libs which I don't have)

Zebee