I just experienced an issue where I upgraded MySQL, and had to reinstall the DBD::Mysql module to match the new client libraries (libmysqlclient.so.10 - I was getting messages about an ISA directive not found). After reinstalling the MySQL module, DBI began to spew errors at me when I tried to restart Apache. I was running mod_perl 1.24, and after reinstalling DBI, I finally figured out that I needed to upgrade mod_perl (I went to mod_perl 1.26) and this fixed the problem.
This is pretty much just a helping piece for anyone searching for this error. - Jonathan
