Strange error with Pg.so

I have a strange error with Pg.so. I have a Perl program that should
run as a CGI script.

Strangely enough, it works if I run it from the command line now (at
least it outputs a html page), but when I try it from my web server it
complains with an error like

[Sat Dec 26 11:02:48 1998] [error] Can't load
'/usr/lib/perl5/site_perl/i586-linux/auto/Pg/Pg.so' for module Pg:
Unable to resolve symbol at
/usr/lib/perl5/i586-linux/5.00404/DynaLoader.pm line 166.

and this is what Dynaloader has to say about it:

    # Many dynamic extension loading problems will appear to come from
    # this section of code: XYZ failed at line 123 of DynaLoader.pm.
    # Often these errors are actually occurring in the initialisation
    # C code of the extension XS file. Perl reports the error as being
    # in this perl code simply because this was the last perl code
    # it executed.

What is surprising for me is that the error only appears when run
through the web server.

It happens before any action is taken; it complains about the "use Pg;"
statement

Well, I'm using PostgreSQL 6.3.2, maybe I should try to install 6.4.1?