Installation of postgresql 6.4.2 + libpq

I have been working with a littlebit older postgres version uptil now
(6.3.1)
I then decided to update everything to 6.4.2
All installation via rpm's on a Linux/Pentium system

I uninstalled the old version
Installed the new.
Then i ran into problems - whenever trying to compile my C programs it
ended with the following error :

   /usr/lib/libpq.so: undefined reference to 'crypt'

Urgh.
Does this mean i have to go back to version 6.3.1 ?
I tried updating all my libraries to the newest libc set (including
libcrypt)

Anyone have any suggestions I will appreciate any input.

Best regards
Jesper K. Pedersen
Just another happy Linux user :-)